/*
* Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*/
package java.lang;
import java.io.
ObjectStreamField;
import java.io.
UnsupportedEncodingException;
import java.nio.charset.
Charset;
import java.util.
ArrayList;
import java.util.
Arrays;
import java.util.
Comparator;
import java.util.
Formatter;
import java.util.
Locale;
import java.util.
Objects;
import java.util.
StringJoiner;
import java.util.regex.
Matcher;
import java.util.regex.
Pattern;
import java.util.regex.
PatternSyntaxException;
/**
* The {@code String} class represents character strings. All
* string literals in Java programs, such as {@code "abc"}, are
* implemented as instances of this class.
* <p>
* Strings are constant; their values cannot be changed after they
* are created. String buffers support mutable strings.
* Because String objects are immutable they can be shared. For example:
* <blockquote><pre>
* String str = "abc";
* </pre></blockquote><p>
* is equivalent to:
* <blockquote><pre>
* char data[] = {'a', 'b', 'c'};
* String str = new String(data);
* </pre></blockquote><p>
* Here are some more examples of how strings can be used:
* <blockquote><pre>
* System.out.println("abc");
* String cde = "cde";
* System.out.println("abc" + cde);
* String c = "abc".substring(2,3);
* String d = cde.substring(1, 2);
* </pre></blockquote>
* <p>
* The class {@code String} includes methods for examining
* individual characters of the sequence, for comparing strings, for
* searching strings, for extracting substrings, and for creating a
* copy of a string with all characters translated to uppercase or to
* lowercase. Case mapping is based on the Unicode Standard version
* specified by the {@link java.lang.Character Character} class.
* <p>
* The Java language provides special support for the string
* concatenation operator ( + ), and for conversion of
* other objects to strings. String concatenation is implemented
* through the {@code StringBuilder}(or {@code StringBuffer})
* class and its {@code append} method.
* String conversions are implemented through the method
* {@code toString}, defined by {@code Object} and
* inherited by all classes in Java. For additional information on
* string concatenation and conversion, see Gosling, Joy, and Steele,
* <i>The Java Language Specification</i>.
*
* <p> Unless otherwise noted, passing a <tt>null</tt> argument to a constructor
* or method in this class will cause a {@link NullPointerException} to be
* thrown.
*
* <p>A {@code String} represents a string in the UTF-16 format
* in which <em>supplementary characters</em> are represented by <em>surrogate
* pairs</em> (see the section <a href="Character.html#unicode">Unicode
* Character Representations</a> in the {@code Character} class for
* more information).
* Index values refer to {@code char} code units, so a supplementary
* character uses two positions in a {@code String}.
* <p>The {@code String} class provides methods for dealing with
* Unicode code points (i.e., characters), in addition to those for
* dealing with Unicode code units (i.e., {@code char} values).
*
* @author Lee Boynton
* @author Arthur van Hoff
* @author Martin Buchholz
* @author Ulf Zibis
* @see java.lang.Object#toString()
* @see java.lang.StringBuffer
* @see java.lang.StringBuilder
* @see java.nio.charset.Charset
* @since JDK1.0
*/
public final class
String
implements java.io.
Serializable,
Comparable<
String>,
CharSequence {
/** The value is used for character storage. */
private final char
value[];
/** Cache the hash code for the string */
private int
hash; // Default to 0
/** use serialVersionUID from JDK 1.0.2 for interoperability */
private static final long
serialVersionUID = -6849794470754667710L;
/**
* Class String is special cased within the Serialization Stream Protocol.
*
* A String instance is written into an ObjectOutputStream according to
* <a href="{@docRoot}/../platform/serialization/spec/output.html">
* Object Serialization Specification, Section 6.2, "Stream Elements"</a>
*/
private static final
ObjectStreamField[]
serialPersistentFields =
new
ObjectStreamField[0];
/**
* Initializes a newly created {@code String} object so that it represents
* an empty character sequence. Note that use of this constructor is
* unnecessary since Strings are immutable.
*/
public
String() {
this.
value = "".
value;
}
/**
* Initializes a newly created {@code String} object so that it represents
* the same sequence of characters as the argument; in other words, the
* newly created string is a copy of the argument string. Unless an
* explicit copy of {@code original} is needed, use of this constructor is
* unnecessary since Strings are immutable.
*
* @param original
* A {@code String}
*/
public
String(
String original) {
this.
value =
original.
value;
this.
hash =
original.
hash;
}
/**
* Allocates a new {@code String} so that it represents the sequence of
* characters currently contained in the character array argument. The
* contents of the character array are copied; subsequent modification of
* the character array does not affect the newly created string.
*
* @param value
* The initial value of the string
*/
public
String(char
value[]) {
this.
value =
Arrays.
copyOf(
value,
value.length);
}
/**
* Allocates a new {@code String} that contains characters from a subarray
* of the character array argument. The {@code offset} argument is the
* index of the first character of the subarray and the {@code count}
* argument specifies the length of the subarray. The contents of the
* subarray are copied; subsequent modification of the character array does
* not affect the newly created string.
*
* @param value
* Array that is the source of characters
*
* @param offset
* The initial offset
*
* @param count
* The length
*
* @throws IndexOutOfBoundsException
* If the {@code offset} and {@code count} arguments index
* characters outside the bounds of the {@code value} array
*/
public
String(char
value[], int
offset, int
count) {
if (
offset < 0) {
throw new
StringIndexOutOfBoundsException(
offset);
}
if (
count <= 0) {
if (
count < 0) {
throw new
StringIndexOutOfBoundsException(
count);
}
if (
offset <=
value.length) {
this.
value = "".
value;
return;
}
}
// Note: offset or count might be near -1>>>1.
if (
offset >
value.length -
count) {
throw new
StringIndexOutOfBoundsException(
offset +
count);
}
this.
value =
Arrays.
copyOfRange(
value,
offset,
offset+
count);
}
/**
* Allocates a new {@code String} that contains characters from a subarray
* of the <a href="Character.html#unicode">Unicode code point</a> array
* argument. The {@code offset} argument is the index of the first code
* point of the subarray and the {@code count} argument specifies the
* length of the subarray. The contents of the subarray are converted to
* {@code char}s; subsequent modification of the {@code int} array does not
* affect the newly created string.
*
* @param codePoints
* Array that is the source of Unicode code points
*
* @param offset
* The initial offset
*
* @param count
* The length
*
* @throws IllegalArgumentException
* If any invalid Unicode code point is found in {@code
* codePoints}
*
* @throws IndexOutOfBoundsException
* If the {@code offset} and {@code count} arguments index
* characters outside the bounds of the {@code codePoints} array
*
* @since 1.5
*/
public
String(int[]
codePoints, int
offset, int
count) {
if (
offset < 0) {
throw new
StringIndexOutOfBoundsException(
offset);
}
if (
count <= 0) {
if (
count < 0) {
throw new
StringIndexOutOfBoundsException(
count);
}
if (
offset <=
codePoints.length) {
this.
value = "".
value;
return;
}
}
// Note: offset or count might be near -1>>>1.
if (
offset >
codePoints.length -
count) {
throw new
StringIndexOutOfBoundsException(
offset +
count);
}
final int
end =
offset +
count;
// Pass 1: Compute precise size of char[]
int
n =
count;
for (int
i =
offset;
i <
end;
i++) {
int
c =
codePoints[
i];
if (
Character.
isBmpCodePoint(
c))
continue;
else if (
Character.
isValidCodePoint(
c))
n++;
else throw new
IllegalArgumentException(
Integer.
toString(
c));
}
// Pass 2: Allocate and fill in char[]
final char[]
v = new char[
n];
for (int
i =
offset,
j = 0;
i <
end;
i++,
j++) {
int
c =
codePoints[
i];
if (
Character.
isBmpCodePoint(
c))
v[
j] = (char)
c;
else
Character.
toSurrogates(
c,
v,
j++);
}
this.
value =
v;
}
/**
* Allocates a new {@code String} constructed from a subarray of an array
* of 8-bit integer values.
*
* <p> The {@code offset} argument is the index of the first byte of the
* subarray, and the {@code count} argument specifies the length of the
* subarray.
*
* <p> Each {@code byte} in the subarray is converted to a {@code char} as
* specified in the method above.
*
* @deprecated This method does not properly convert bytes into characters.
* As of JDK 1.1, the preferred way to do this is via the
* {@code String} constructors that take a {@link
* java.nio.charset.Charset}, charset name, or that use the platform's
* default charset.
*
* @param ascii
* The bytes to be converted to characters
*
* @param hibyte
* The top 8 bits of each 16-bit Unicode code unit
*
* @param offset
* The initial offset
* @param count
* The length
*
* @throws IndexOutOfBoundsException
* If the {@code offset} or {@code count} argument is invalid
*
* @see #String(byte[], int)
* @see #String(byte[], int, int, java.lang.String)
* @see #String(byte[], int, int, java.nio.charset.Charset)
* @see #String(byte[], int, int)
* @see #String(byte[], java.lang.String)
* @see #String(byte[], java.nio.charset.Charset)
* @see #String(byte[])
*/
@
Deprecated
public
String(byte
ascii[], int
hibyte, int
offset, int
count) {
checkBounds(
ascii,
offset,
count);
char
value[] = new char[
count];
if (
hibyte == 0) {
for (int
i =
count;
i-- > 0;) {
value[
i] = (char)(
ascii[
i +
offset] & 0xff);
}
} else {
hibyte <<= 8;
for (int
i =
count;
i-- > 0;) {
value[
i] = (char)(
hibyte | (
ascii[
i +
offset] & 0xff));
}
}
this.
value =
value;
}
/**
* Allocates a new {@code String} containing characters constructed from
* an array of 8-bit integer values. Each character <i>c</i>in the
* resulting string is constructed from the corresponding component
* <i>b</i> in the byte array such that:
*
* <blockquote><pre>
* <b><i>c</i></b> == (char)(((hibyte & 0xff) << 8)
* | (<b><i>b</i></b> & 0xff))
* </pre></blockquote>
*
* @deprecated This method does not properly convert bytes into
* characters. As of JDK 1.1, the preferred way to do this is via the
* {@code String} constructors that take a {@link
* java.nio.charset.Charset}, charset name, or that use the platform's
* default charset.
*
* @param ascii
* The bytes to be converted to characters
*
* @param hibyte
* The top 8 bits of each 16-bit Unicode code unit
*
* @see #String(byte[], int, int, java.lang.String)
* @see #String(byte[], int, int, java.nio.charset.Charset)
* @see #String(byte[], int, int)
* @see #String(byte[], java.lang.String)
* @see #String(byte[], java.nio.charset.Charset)
* @see #String(byte[])
*/
@
Deprecated
public
String(byte
ascii[], int
hibyte) {
this(
ascii,
hibyte, 0,
ascii.length);
}
/* Common private utility method used to bounds check the byte array
* and requested offset & length values used by the String(byte[],..)
* constructors.
*/
private static void
checkBounds(byte[]
bytes, int
offset, int
length) {
if (
length < 0)
throw new
StringIndexOutOfBoundsException(
length);
if (
offset < 0)
throw new
StringIndexOutOfBoundsException(
offset);
if (
offset >
bytes.length -
length)
throw new
StringIndexOutOfBoundsException(
offset +
length);
}
/**
* Constructs a new {@code String} by decoding the specified subarray of
* bytes using the specified charset. The length of the new {@code String}
* is a function of the charset, and hence may not be equal to the length
* of the subarray.
*
* <p> The behavior of this constructor when the given bytes are not valid
* in the given charset is unspecified. The {@link
* java.nio.charset.CharsetDecoder} class should be used when more control
* over the decoding process is required.
*
* @param bytes
* The bytes to be decoded into characters
*
* @param offset
* The index of the first byte to decode
*
* @param length
* The number of bytes to decode
* @param charsetName
* The name of a supported {@linkplain java.nio.charset.Charset
* charset}
*
* @throws UnsupportedEncodingException
* If the named charset is not supported
*
* @throws IndexOutOfBoundsException
* If the {@code offset} and {@code length} arguments index
* characters outside the bounds of the {@code bytes} array
*
* @since JDK1.1
*/
public
String(byte
bytes[], int
offset, int
length,
String charsetName)
throws
UnsupportedEncodingException {
if (
charsetName == null)
throw new
NullPointerException("charsetName");
checkBounds(
bytes,
offset,
length);
this.
value =
StringCoding.
decode(
charsetName,
bytes,
offset,
length);
}
/**
* Constructs a new {@code String} by decoding the specified subarray of
* bytes using the specified {@linkplain java.nio.charset.Charset charset}.
* The length of the new {@code String} is a function of the charset, and
* hence may not be equal to the length of the subarray.
*
* <p> This method always replaces malformed-input and unmappable-character
* sequences with this charset's default replacement string. The {@link
* java.nio.charset.CharsetDecoder} class should be used when more control
* over the decoding process is required.
*
* @param bytes
* The bytes to be decoded into characters
*
* @param offset
* The index of the first byte to decode
*
* @param length
* The number of bytes to decode
*
* @param charset
* The {@linkplain java.nio.charset.Charset charset} to be used to
* decode the {@code bytes}
*
* @throws IndexOutOfBoundsException
* If the {@code offset} and {@code length} arguments index
* characters outside the bounds of the {@code bytes} array
*
* @since 1.6
*/
public
String(byte
bytes[], int
offset, int
length,
Charset charset) {
if (
charset == null)
throw new
NullPointerException("charset");
checkBounds(
bytes,
offset,
length);
this.
value =
StringCoding.
decode(
charset,
bytes,
offset,
length);
}
/**
* Constructs a new {@code String} by decoding the specified array of bytes
* using the specified {@linkplain java.nio.charset.Charset charset}. The
* length of the new {@code String} is a function of the charset, and hence
* may not be equal to the length of the byte array.
*
* <p> The behavior of this constructor when the given bytes are not valid
* in the given charset is unspecified. The {@link
* java.nio.charset.CharsetDecoder} class should be used when more control
* over the decoding process is required.
*
* @param bytes
* The bytes to be decoded into characters
*
* @param charsetName
* The name of a supported {@linkplain java.nio.charset.Charset
* charset}
*
* @throws UnsupportedEncodingException
* If the named charset is not supported
*
* @since JDK1.1
*/
public
String(byte
bytes[],
String charsetName)
throws
UnsupportedEncodingException {
this(
bytes, 0,
bytes.length,
charsetName);
}
/**
* Constructs a new {@code String} by decoding the specified array of
* bytes using the specified {@linkplain java.nio.charset.Charset charset}.
* The length of the new {@code String} is a function of the charset, and
* hence may not be equal to the length of the byte array.
*
* <p> This method always replaces malformed-input and unmappable-character
* sequences with this charset's default replacement string. The {@link
* java.nio.charset.CharsetDecoder} class should be used when more control
* over the decoding process is required.
*
* @param bytes
* The bytes to be decoded into characters
*
* @param charset
* The {@linkplain java.nio.charset.Charset charset} to be used to
* decode the {@code bytes}
*
* @since 1.6
*/
public
String(byte
bytes[],
Charset charset) {
this(
bytes, 0,
bytes.length,
charset);
}
/**
* Constructs a new {@code String} by decoding the specified subarray of
* bytes using the platform's default charset. The length of the new
* {@code String} is a function of the charset, and hence may not be equal
* to the length of the subarray.
*
* <p> The behavior of this constructor when the given bytes are not valid
* in the default charset is unspecified. The {@link
* java.nio.charset.CharsetDecoder} class should be used when more control
* over the decoding process is required.
*
* @param bytes
* The bytes to be decoded into characters
*
* @param offset
* The index of the first byte to decode
*
* @param length
* The number of bytes to decode
*
* @throws IndexOutOfBoundsException
* If the {@code offset} and the {@code length} arguments index
* characters outside the bounds of the {@code bytes} array
*
* @since JDK1.1
*/
public
String(byte
bytes[], int
offset, int
length) {
checkBounds(
bytes,
offset,
length);
this.
value =
StringCoding.
decode(
bytes,
offset,
length);
}
/**
* Constructs a new {@code String} by decoding the specified array of bytes
* using the platform's default charset. The length of the new {@code
* String} is a function of the charset, and hence may not be equal to the
* length of the byte array.
*
* <p> The behavior of this constructor when the given bytes are not valid
* in the default charset is unspecified. The {@link
* java.nio.charset.CharsetDecoder} class should be used when more control
* over the decoding process is required.
*
* @param bytes
* The bytes to be decoded into characters
*
* @since JDK1.1
*/
public
String(byte
bytes[]) {
this(
bytes, 0,
bytes.length);
}
/**
* Allocates a new string that contains the sequence of characters
* currently contained in the string buffer argument. The contents of the
* string buffer are copied; subsequent modification of the string buffer
* does not affect the newly created string.
*
* @param buffer
* A {@code StringBuffer}
*/
public
String(
StringBuffer buffer) {
synchronized(
buffer) {
this.
value =
Arrays.
copyOf(
buffer.
getValue(),
buffer.
length());
}
}
/**
* Allocates a new string that contains the sequence of characters
* currently contained in the string builder argument. The contents of the
* string builder are copied; subsequent modification of the string builder
* does not affect the newly created string.
*
* <p> This constructor is provided to ease migration to {@code
* StringBuilder}. Obtaining a string from a string builder via the {@code
* toString} method is likely to run faster and is generally preferred.
*
* @param builder
* A {@code StringBuilder}
*
* @since 1.5
*/
public
String(
StringBuilder builder) {
this.
value =
Arrays.
copyOf(
builder.
getValue(),
builder.
length());
}
/*
* Package private constructor which shares value array for speed.
* this constructor is always expected to be called with share==true.
* a separate constructor is needed because we already have a public
* String(char[]) constructor that makes a copy of the given char[].
*/
String(char[]
value, boolean
share) {
// assert share : "unshared not supported";
this.
value =
value;
}
/**
* Returns the length of this string.
* The length is equal to the number of <a href="Character.html#unicode">Unicode
* code units</a> in the string.
*
* @return the length of the sequence of characters represented by this
* object.
*/
public int
length() {
return
value.length;
}
/**
* Returns {@code true} if, and only if, {@link #length()} is {@code 0}.
*
* @return {@code true} if {@link #length()} is {@code 0}, otherwise
* {@code false}
*
* @since 1.6
*/
public boolean
isEmpty() {
return
value.length == 0;
}
/**
* Returns the {@code char} value at the
* specified index. An index ranges from {@code 0} to
* {@code length() - 1}. The first {@code char} value of the sequence
* is at index {@code 0}, the next at index {@code 1},
* and so on, as for array indexing.
*
* <p>If the {@code char} value specified by the index is a
* <a href="Character.html#unicode">surrogate</a>, the surrogate
* value is returned.
*
* @param index the index of the {@code char} value.
* @return the {@code char} value at the specified index of this string.
* The first {@code char} value is at index {@code 0}.
* @exception IndexOutOfBoundsException if the {@code index}
* argument is negative or not less than the length of this
* string.
*/
public char
charAt(int
index) {
if ((
index < 0) || (
index >=
value.length)) {
throw new
StringIndexOutOfBoundsException(
index);
}
return
value[
index];
}
/**
* Returns the character (Unicode code point) at the specified
* index. The index refers to {@code char} values
* (Unicode code units) and ranges from {@code 0} to
* {@link #length()}{@code - 1}.
*
* <p> If the {@code char} value specified at the given index
* is in the high-surrogate range, the following index is less
* than the length of this {@code String}, and the
* {@code char} value at the following index is in the
* low-surrogate range, then the supplementary code point
* corresponding to this surrogate pair is returned. Otherwise,
* the {@code char} value at the given index is returned.
*
* @param index the index to the {@code char} values
* @return the code point value of the character at the
* {@code index}
* @exception IndexOutOfBoundsException if the {@code index}
* argument is negative or not less than the length of this
* string.
* @since 1.5
*/
public int
codePointAt(int
index) {
if ((
index < 0) || (
index >=
value.length)) {
throw new
StringIndexOutOfBoundsException(
index);
}
return
Character.
codePointAtImpl(
value,
index,
value.length);
}
/**
* Returns the character (Unicode code point) before the specified
* index. The index refers to {@code char} values
* (Unicode code units) and ranges from {@code 1} to {@link
* CharSequence#length() length}.
*
* <p> If the {@code char} value at {@code (index - 1)}
* is in the low-surrogate range, {@code (index - 2)} is not
* negative, and the {@code char} value at {@code (index -
* 2)} is in the high-surrogate range, then the
* supplementary code point value of the surrogate pair is
* returned. If the {@code char} value at {@code index -
* 1} is an unpaired low-surrogate or a high-surrogate, the
* surrogate value is returned.
*
* @param index the index following the code point that should be returned
* @return the Unicode code point value before the given index.
* @exception IndexOutOfBoundsException if the {@code index}
* argument is less than 1 or greater than the length
* of this string.
* @since 1.5
*/
public int
codePointBefore(int
index) {
int
i =
index - 1;
if ((
i < 0) || (
i >=
value.length)) {
throw new
StringIndexOutOfBoundsException(
index);
}
return
Character.
codePointBeforeImpl(
value,
index, 0);
}
/**
* Returns the number of Unicode code points in the specified text
* range of this {@code String}. The text range begins at the
* specified {@code beginIndex} and extends to the
* {@code char} at index {@code endIndex - 1}. Thus the
* length (in {@code char}s) of the text range is
* {@code endIndex-beginIndex}. Unpaired surrogates within
* the text range count as one code point each.
*
* @param beginIndex the index to the first {@code char} of
* the text range.
* @param endIndex the index after the last {@code char} of
* the text range.
* @return the number of Unicode code points in the specified text
* range
* @exception IndexOutOfBoundsException if the
* {@code beginIndex} is negative, or {@code endIndex}
* is larger than the length of this {@code String}, or
* {@code beginIndex} is larger than {@code endIndex}.
* @since 1.5
*/
public int
codePointCount(int
beginIndex, int
endIndex) {
if (
beginIndex < 0 ||
endIndex >
value.length ||
beginIndex >
endIndex) {
throw new
IndexOutOfBoundsException();
}
return
Character.
codePointCountImpl(
value,
beginIndex,
endIndex -
beginIndex);
}
/**
* Returns the index within this {@code String} that is
* offset from the given {@code index} by
* {@code codePointOffset} code points. Unpaired surrogates
* within the text range given by {@code index} and
* {@code codePointOffset} count as one code point each.
*
* @param index the index to be offset
* @param codePointOffset the offset in code points
* @return the index within this {@code String}
* @exception IndexOutOfBoundsException if {@code index}
* is negative or larger then the length of this
* {@code String}, or if {@code codePointOffset} is positive
* and the substring starting with {@code index} has fewer
* than {@code codePointOffset} code points,
* or if {@code codePointOffset} is negative and the substring
* before {@code index} has fewer than the absolute value
* of {@code codePointOffset} code points.
* @since 1.5
*/
public int
offsetByCodePoints(int
index, int
codePointOffset) {
if (
index < 0 ||
index >
value.length) {
throw new
IndexOutOfBoundsException();
}
return
Character.
offsetByCodePointsImpl(
value, 0,
value.length,
index,
codePointOffset);
}
/**
* Copy characters from this string into dst starting at dstBegin.
* This method doesn't perform any range checking.
*/
void
getChars(char
dst[], int
dstBegin) {
System.
arraycopy(
value, 0,
dst,
dstBegin,
value.length);
}
/**
* Copies characters from this string into the destination character
* array.
* <p>
* The first character to be copied is at index {@code srcBegin};
* the last character to be copied is at index {@code srcEnd-1}
* (thus the total number of characters to be copied is
* {@code srcEnd-srcBegin}). The characters are copied into the
* subarray of {@code dst} starting at index {@code dstBegin}
* and ending at index:
* <blockquote><pre>
* dstBegin + (srcEnd-srcBegin) - 1
* </pre></blockquote>
*
* @param srcBegin index of the first character in the string
* to copy.
* @param srcEnd index after the last character in the string
* to copy.
* @param dst the destination array.
* @param dstBegin the start offset in the destination array.
* @exception IndexOutOfBoundsException If any of the following
* is true:
* <ul><li>{@code srcBegin} is negative.
* <li>{@code srcBegin} is greater than {@code srcEnd}
* <li>{@code srcEnd} is greater than the length of this
* string
* <li>{@code dstBegin} is negative
* <li>{@code dstBegin+(srcEnd-srcBegin)} is larger than
* {@code dst.length}</ul>
*/
public void
getChars(int
srcBegin, int
srcEnd, char
dst[], int
dstBegin) {
if (
srcBegin < 0) {
throw new
StringIndexOutOfBoundsException(
srcBegin);
}
if (
srcEnd >
value.length) {
throw new
StringIndexOutOfBoundsException(
srcEnd);
}
if (
srcBegin >
srcEnd) {
throw new
StringIndexOutOfBoundsException(
srcEnd -
srcBegin);
}
System.
arraycopy(
value,
srcBegin,
dst,
dstBegin,
srcEnd -
srcBegin);
}
/**
* Copies characters from this string into the destination byte array. Each
* byte receives the 8 low-order bits of the corresponding character. The
* eight high-order bits of each character are not copied and do not
* participate in the transfer in any way.
*
* <p> The first character to be copied is at index {@code srcBegin}; the
* last character to be copied is at index {@code srcEnd-1}. The total
* number of characters to be copied is {@code srcEnd-srcBegin}. The
* characters, converted to bytes, are copied into the subarray of {@code
* dst} starting at index {@code dstBegin} and ending at index:
*
* <blockquote><pre>
* dstBegin + (srcEnd-srcBegin) - 1
* </pre></blockquote>
*
* @deprecated This method does not properly convert characters into
* bytes. As of JDK 1.1, the preferred way to do this is via the
* {@link #getBytes()} method, which uses the platform's default charset.
*
* @param srcBegin
* Index of the first character in the string to copy
*
* @param srcEnd
* Index after the last character in the string to copy
*
* @param dst
* The destination array
*
* @param dstBegin
* The start offset in the destination array
*
* @throws IndexOutOfBoundsException
* If any of the following is true:
* <ul>
* <li> {@code srcBegin} is negative
* <li> {@code srcBegin} is greater than {@code srcEnd}
* <li> {@code srcEnd} is greater than the length of this String
* <li> {@code dstBegin} is negative
* <li> {@code dstBegin+(srcEnd-srcBegin)} is larger than {@code
* dst.length}
* </ul>
*/
@
Deprecated
public void
getBytes(int
srcBegin, int
srcEnd, byte
dst[], int
dstBegin) {
if (
srcBegin < 0) {
throw new
StringIndexOutOfBoundsException(
srcBegin);
}
if (
srcEnd >
value.length) {
throw new
StringIndexOutOfBoundsException(
srcEnd);
}
if (
srcBegin >
srcEnd) {
throw new
StringIndexOutOfBoundsException(
srcEnd -
srcBegin);
}
Objects.
requireNonNull(
dst);
int
j =
dstBegin;
int
n =
srcEnd;
int
i =
srcBegin;
char[]
val =
value; /* avoid getfield opcode */
while (
i <
n) {
dst[
j++] = (byte)
val[
i++];
}
}
/**
* Encodes this {@code String} into a sequence of bytes using the named
* charset, storing the result into a new byte array.
*
* <p> The behavior of this method when this string cannot be encoded in
* the given charset is unspecified. The {@link
* java.nio.charset.CharsetEncoder} class should be used when more control
* over the encoding process is required.
*
* @param charsetName
* The name of a supported {@linkplain java.nio.charset.Charset
* charset}
*
* @return The resultant byte array
*
* @throws UnsupportedEncodingException
* If the named charset is not supported
*
* @since JDK1.1
*/
public byte[]
getBytes(
String charsetName)
throws
UnsupportedEncodingException {
if (
charsetName == null) throw new
NullPointerException();
return
StringCoding.
encode(
charsetName,
value, 0,
value.length);
}
/**
* Encodes this {@code String} into a sequence of bytes using the given
* {@linkplain java.nio.charset.Charset charset}, storing the result into a
* new byte array.
*
* <p> This method always replaces malformed-input and unmappable-character
* sequences with this charset's default replacement byte array. The
* {@link java.nio.charset.CharsetEncoder} class should be used when more
* control over the encoding process is required.
*
* @param charset
* The {@linkplain java.nio.charset.Charset} to be used to encode
* the {@code String}
*
* @return The resultant byte array
*
* @since 1.6
*/
public byte[]
getBytes(
Charset charset) {
if (
charset == null) throw new
NullPointerException();
return
StringCoding.
encode(
charset,
value, 0,
value.length);
}
/**
* Encodes this {@code String} into a sequence of bytes using the
* platform's default charset, storing the result into a new byte array.
*
* <p> The behavior of this method when this string cannot be encoded in
* the default charset is unspecified. The {@link
* java.nio.charset.CharsetEncoder} class should be used when more control
* over the encoding process is required.
*
* @return The resultant byte array
*
* @since JDK1.1
*/
public byte[]
getBytes() {
return
StringCoding.
encode(
value, 0,
value.length);
}
/**
* Compares this string to the specified object. The result is {@code
* true} if and only if the argument is not {@code null} and is a {@code
* String} object that represents the same sequence of characters as this
* object.
*
* @param anObject
* The object to compare this {@code String} against
*
* @return {@code true} if the given object represents a {@code String}
* equivalent to this string, {@code false} otherwise
*
* @see #compareTo(String)
* @see #equalsIgnoreCase(String)
*/
public boolean
equals(
Object anObject) {
if (this ==
anObject) {
return true;
}
if (
anObject instanceof
String) {
String anotherString = (
String)
anObject;
int
n =
value.length;
if (
n ==
anotherString.
value.length) {
char
v1[] =
value;
char
v2[] =
anotherString.
value;
int
i = 0;
while (
n-- != 0) {
if (
v1[
i] !=
v2[
i])
return false;
i++;
}
return true;
}
}
return false;
}
/**
* Compares this string to the specified {@code StringBuffer}. The result
* is {@code true} if and only if this {@code String} represents the same
* sequence of characters as the specified {@code StringBuffer}. This method
* synchronizes on the {@code StringBuffer}.
*
* @param sb
* The {@code StringBuffer} to compare this {@code String} against
*
* @return {@code true} if this {@code String} represents the same
* sequence of characters as the specified {@code StringBuffer},
* {@code false} otherwise
*
* @since 1.4
*/
public boolean
contentEquals(
StringBuffer sb) {
return
contentEquals((
CharSequence)
sb);
}
private boolean
nonSyncContentEquals(
AbstractStringBuilder sb) {
char
v1[] =
value;
char
v2[] =
sb.
getValue();
int
n =
v1.length;
if (
n !=
sb.
length()) {
return false;
}
for (int
i = 0;
i <
n;
i++) {
if (
v1[
i] !=
v2[
i]) {
return false;
}
}
return true;
}
/**
* Compares this string to the specified {@code CharSequence}. The
* result is {@code true} if and only if this {@code String} represents the
* same sequence of char values as the specified sequence. Note that if the
* {@code CharSequence} is a {@code StringBuffer} then the method
* synchronizes on it.
*
* @param cs
* The sequence to compare this {@code String} against
*
* @return {@code true} if this {@code String} represents the same
* sequence of char values as the specified sequence, {@code
* false} otherwise
*
* @since 1.5
*/
public boolean
contentEquals(
CharSequence cs) {
// Argument is a StringBuffer, StringBuilder
if (
cs instanceof
AbstractStringBuilder) {
if (
cs instanceof
StringBuffer) {
synchronized(
cs) {
return
nonSyncContentEquals((
AbstractStringBuilder)
cs);
}
} else {
return
nonSyncContentEquals((
AbstractStringBuilder)
cs);
}
}
// Argument is a String
if (
cs instanceof
String) {
return
equals(
cs);
}
// Argument is a generic CharSequence
char
v1[] =
value;
int
n =
v1.length;
if (
n !=
cs.
length()) {
return false;
}
for (int
i = 0;
i <
n;
i++) {
if (
v1[
i] !=
cs.
charAt(
i)) {
return false;
}
}
return true;
}
/**
* Compares this {@code String} to another {@code String}, ignoring case
* considerations. Two strings are considered equal ignoring case if they
* are of the same length and corresponding characters in the two strings
* are equal ignoring case.
*
* <p> Two characters {@code c1} and {@code c2} are considered the same
* ignoring case if at least one of the following is true:
* <ul>
* <li> The two characters are the same (as compared by the
* {@code ==} operator)
* <li> Applying the method {@link
* java.lang.Character#toUpperCase(char)} to each character
* produces the same result
* <li> Applying the method {@link
* java.lang.Character#toLowerCase(char)} to each character
* produces the same result
* </ul>
*
* @param anotherString
* The {@code String} to compare this {@code String} against
*
* @return {@code true} if the argument is not {@code null} and it
* represents an equivalent {@code String} ignoring case; {@code
* false} otherwise
*
* @see #equals(Object)
*/
public boolean
equalsIgnoreCase(
String anotherString) {
return (this ==
anotherString) ? true
: (
anotherString != null)
&& (
anotherString.
value.length ==
value.length)
&&
regionMatches(true, 0,
anotherString, 0,
value.length);
}
/**
* Compares two strings lexicographically.
* The comparison is based on the Unicode value of each character in
* the strings. The character sequence represented by this
* {@code String} object is compared lexicographically to the
* character sequence represented by the argument string. The result is
* a negative integer if this {@code String} object
* lexicographically precedes the argument string. The result is a
* positive integer if this {@code String} object lexicographically
* follows the argument string. The result is zero if the strings
* are equal; {@code compareTo} returns {@code 0} exactly when
* the {@link #equals(Object)} method would return {@code true}.
* <p>
* This is the definition of lexicographic ordering. If two strings are
* different, then either they have different characters at some index
* that is a valid index for both strings, or their lengths are different,
* or both. If they have different characters at one or more index
* positions, let <i>k</i> be the smallest such index; then the string
* whose character at position <i>k</i> has the smaller value, as
* determined by using the < operator, lexicographically precedes the
* other string. In this case, {@code compareTo} returns the
* difference of the two character values at position {@code k} in
* the two string -- that is, the value:
* <blockquote><pre>
* this.charAt(k)-anotherString.charAt(k)
* </pre></blockquote>
* If there is no index position at which they differ, then the shorter
* string lexicographically precedes the longer string. In this case,
* {@code compareTo} returns the difference of the lengths of the
* strings -- that is, the value:
* <blockquote><pre>
* this.length()-anotherString.length()
* </pre></blockquote>
*
* @param anotherString the {@code String} to be compared.
* @return the value {@code 0} if the argument string is equal to
* this string; a value less than {@code 0} if this string
* is lexicographically less than the string argument; and a
* value greater than {@code 0} if this string is
* lexicographically greater than the string argument.
*/
public int
compareTo(
String anotherString) {
int
len1 =
value.length;
int
len2 =
anotherString.
value.length;
int
lim =
Math.
min(
len1,
len2);
char
v1[] =
value;
char
v2[] =
anotherString.
value;
int
k = 0;
while (
k <
lim) {
char
c1 =
v1[
k];
char
c2 =
v2[
k];
if (
c1 !=
c2) {
return
c1 -
c2;
}
k++;
}
return
len1 -
len2;
}
/**
* A Comparator that orders {@code String} objects as by
* {@code compareToIgnoreCase}. This comparator is serializable.
* <p>
* Note that this Comparator does <em>not</em> take locale into account,
* and will result in an unsatisfactory ordering for certain locales.
* The java.text package provides <em>Collators</em> to allow
* locale-sensitive ordering.
*
* @see java.text.Collator#compare(String, String)
* @since 1.2
*/
public static final
Comparator<
String>
CASE_INSENSITIVE_ORDER
= new
CaseInsensitiveComparator();
private static class
CaseInsensitiveComparator
implements
Comparator<
String>, java.io.
Serializable {
// use serialVersionUID from JDK 1.2.2 for interoperability
private static final long
serialVersionUID = 8575799808933029326L;
public int
compare(
String s1,
String s2) {
int
n1 =
s1.
length();
int
n2 =
s2.
length();
int
min =
Math.
min(
n1,
n2);
for (int
i = 0;
i <
min;
i++) {
char
c1 =
s1.
charAt(
i);
char
c2 =
s2.
charAt(
i);
if (
c1 !=
c2) {
c1 =
Character.
toUpperCase(
c1);
c2 =
Character.
toUpperCase(
c2);
if (
c1 !=
c2) {
c1 =
Character.
toLowerCase(
c1);
c2 =
Character.
toLowerCase(
c2);
if (
c1 !=
c2) {
// No overflow because of numeric promotion
return
c1 -
c2;
}
}
}
}
return
n1 -
n2;
}
/** Replaces the de-serialized object. */
private
Object readResolve() { return
CASE_INSENSITIVE_ORDER; }
}
/**
* Compares two strings lexicographically, ignoring case
* differences. This method returns an integer whose sign is that of
* calling {@code compareTo} with normalized versions of the strings
* where case differences have been eliminated by calling
* {@code Character.toLowerCase(Character.toUpperCase(character))} on
* each character.
* <p>
* Note that this method does <em>not</em> take locale into account,
* and will result in an unsatisfactory ordering for certain locales.
* The java.text package provides <em>collators</em> to allow
* locale-sensitive ordering.
*
* @param str the {@code String} to be compared.
* @return a negative integer, zero, or a positive integer as the
* specified String is greater than, equal to, or less
* than this String, ignoring case considerations.
* @see java.text.Collator#compare(String, String)
* @since 1.2
*/
public int
compareToIgnoreCase(
String str) {
return
CASE_INSENSITIVE_ORDER.
compare(this,
str);
}
/**
* Tests if two string regions are equal.
* <p>
* A substring of this {@code String} object is compared to a substring
* of the argument other. The result is true if these substrings
* represent identical character sequences. The substring of this
* {@code String} object to be compared begins at index {@code toffset}
* and has length {@code len}. The substring of other to be compared
* begins at index {@code ooffset} and has length {@code len}. The
* result is {@code false} if and only if at least one of the following
* is true:
* <ul><li>{@code toffset} is negative.
* <li>{@code ooffset} is negative.
* <li>{@code toffset+len} is greater than the length of this
* {@code String} object.
* <li>{@code ooffset+len} is greater than the length of the other
* argument.
* <li>There is some nonnegative integer <i>k</i> less than {@code len}
* such that:
* {@code this.charAt(toffset + }<i>k</i>{@code ) != other.charAt(ooffset + }
* <i>k</i>{@code )}
* </ul>
*
* @param toffset the starting offset of the subregion in this string.
* @param other the string argument.
* @param ooffset the starting offset of the subregion in the string
* argument.
* @param len the number of characters to compare.
* @return {@code true} if the specified subregion of this string
* exactly matches the specified subregion of the string argument;
* {@code false} otherwise.
*/
public boolean
regionMatches(int
toffset,
String other, int
ooffset,
int
len) {
char
ta[] =
value;
int
to =
toffset;
char
pa[] =
other.
value;
int
po =
ooffset;
// Note: toffset, ooffset, or len might be near -1>>>1.
if ((
ooffset < 0) || (
toffset < 0)
|| (
toffset > (long)
value.length -
len)
|| (
ooffset > (long)
other.
value.length -
len)) {
return false;
}
while (
len-- > 0) {
if (
ta[
to++] !=
pa[
po++]) {
return false;
}
}
return true;
}
/**
* Tests if two string regions are equal.
* <p>
* A substring of this {@code String} object is compared to a substring
* of the argument {@code other}. The result is {@code true} if these
* substrings represent character sequences that are the same, ignoring
* case if and only if {@code ignoreCase} is true. The substring of
* this {@code String} object to be compared begins at index
* {@code toffset} and has length {@code len}. The substring of
* {@code other} to be compared begins at index {@code ooffset} and
* has length {@code len}. The result is {@code false} if and only if
* at least one of the following is true:
* <ul><li>{@code toffset} is negative.
* <li>{@code ooffset} is negative.
* <li>{@code toffset+len} is greater than the length of this
* {@code String} object.
* <li>{@code ooffset+len} is greater than the length of the other
* argument.
* <li>{@code ignoreCase} is {@code false} and there is some nonnegative
* integer <i>k</i> less than {@code len} such that:
* <blockquote><pre>
* this.charAt(toffset+k) != other.charAt(ooffset+k)
* </pre></blockquote>
* <li>{@code ignoreCase} is {@code true} and there is some nonnegative
* integer <i>k</i> less than {@code len} such that:
* <blockquote><pre>
* Character.toLowerCase(this.charAt(toffset+k)) !=
Character.toLowerCase(other.charAt(ooffset+k))
* </pre></blockquote>
* and:
* <blockquote><pre>
* Character.toUpperCase(this.charAt(toffset+k)) !=
* Character.toUpperCase(other.charAt(ooffset+k))
* </pre></blockquote>
* </ul>
*
* @param ignoreCase if {@code true}, ignore case when comparing
* characters.
* @param toffset the starting offset of the subregion in this
* string.
* @param other the string argument.
* @param ooffset the starting offset of the subregion in the string
* argument.
* @param len the number of characters to compare.
* @return {@code true} if the specified subregion of this string
* matches the specified subregion of the string argument;
* {@code false} otherwise. Whether the matching is exact
* or case insensitive depends on the {@code ignoreCase}
* argument.
*/
public boolean
regionMatches(boolean
ignoreCase, int
toffset,
String other, int
ooffset, int
len) {
char
ta[] =
value;
int
to =
toffset;
char
pa[] =
other.
value;
int
po =
ooffset;
// Note: toffset, ooffset, or len might be near -1>>>1.
if ((
ooffset < 0) || (
toffset < 0)
|| (
toffset > (long)
value.length -
len)
|| (
ooffset > (long)
other.
value.length -
len)) {
return false;
}
while (
len-- > 0) {
char
c1 =
ta[
to++];
char
c2 =
pa[
po++];
if (
c1 ==
c2) {
continue;
}
if (
ignoreCase) {
// If characters don't match but case may be ignored,
// try converting both characters to uppercase.
// If the results match, then the comparison scan should
// continue.
char
u1 =
Character.
toUpperCase(
c1);
char
u2 =
Character.
toUpperCase(
c2);
if (
u1 ==
u2) {
continue;
}
// Unfortunately, conversion to uppercase does not work properly
// for the Georgian alphabet, which has strange rules about case
// conversion. So we need to make one last check before
// exiting.
if (
Character.
toLowerCase(
u1) ==
Character.
toLowerCase(
u2)) {
continue;
}
}
return false;
}
return true;
}
/**
* Tests if the substring of this string beginning at the
* specified index starts with the specified prefix.
*
* @param prefix the prefix.
* @param toffset where to begin looking in this string.
* @return {@code true} if the character sequence represented by the
* argument is a prefix of the substring of this object starting
* at index {@code toffset}; {@code false} otherwise.
* The result is {@code false} if {@code toffset} is
* negative or greater than the length of this
* {@code String} object; otherwise the result is the same
* as the result of the expression
* <pre>
* this.substring(toffset).startsWith(prefix)
* </pre>
*/
public boolean
startsWith(
String prefix, int
toffset) {
char
ta[] =
value;
int
to =
toffset;
char
pa[] =
prefix.
value;
int
po = 0;
int
pc =
prefix.
value.length;
// Note: toffset might be near -1>>>1.
if ((
toffset < 0) || (
toffset >
value.length -
pc)) {
return false;
}
while (--
pc >= 0) {
if (
ta[
to++] !=
pa[
po++]) {
return false;
}
}
return true;
}
/**
* Tests if this string starts with the specified prefix.
*
* @param prefix the prefix.
* @return {@code true} if the character sequence represented by the
* argument is a prefix of the character sequence represented by
* this string; {@code false} otherwise.
* Note also that {@code true} will be returned if the
* argument is an empty string or is equal to this
* {@code String} object as determined by the
* {@link #equals(Object)} method.
* @since 1. 0
*/
public boolean
startsWith(
String prefix) {
return
startsWith(
prefix, 0);
}
/**
* Tests if this string ends with the specified suffix.
*
* @param suffix the suffix.
* @return {@code true} if the character sequence represented by the
* argument is a suffix of the character sequence represented by
* this object; {@code false} otherwise. Note that the
* result will be {@code true} if the argument is the
* empty string or is equal to this {@code String} object
* as determined by the {@link #equals(Object)} method.
*/
public boolean
endsWith(
String suffix) {
return
startsWith(
suffix,
value.length -
suffix.
value.length);
}
/**
* Returns a hash code for this string. The hash code for a
* {@code String} object is computed as
* <blockquote><pre>
* s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
* </pre></blockquote>
* using {@code int} arithmetic, where {@code s[i]} is the
* <i>i</i>th character of the string, {@code n} is the length of
* the string, and {@code ^} indicates exponentiation.
* (The hash value of the empty string is zero.)
*
* @return a hash code value for this object.
*/
public int
hashCode() {
int
h =
hash;
if (
h == 0 &&
value.length > 0) {
char
val[] =
value;
for (int
i = 0;
i <
value.length;
i++) {
h = 31 *
h +
val[
i];
}
hash =
h;
}
return
h;
}
/**
* Returns the index within this string of the first occurrence of
* the specified character. If a character with value
* {@code ch} occurs in the character sequence represented by
* this {@code String} object, then the index (in Unicode
* code units) of the first such occurrence is returned. For
* values of {@code ch} in the range from 0 to 0xFFFF
* (inclusive), this is the smallest value <i>k</i> such that:
* <blockquote><pre>
* this.charAt(<i>k</i>) == ch
* </pre></blockquote>
* is true. For other values of {@code ch}, it is the
* smallest value <i>k</i> such that:
* <blockquote><pre>
* this.codePointAt(<i>k</i>) == ch
* </pre></blockquote>
* is true. In either case, if no such character occurs in this
* string, then {@code -1} is returned.
*
* @param ch a character (Unicode code point).
* @return the index of the first occurrence of the character in the
* character sequence represented by this object, or
* {@code -1} if the character does not occur.
*/
public int
indexOf(int
ch) {
return
indexOf(
ch, 0);
}
/**
* Returns the index within this string of the first occurrence of the
* specified character, starting the search at the specified index.
* <p>
* If a character with value {@code ch} occurs in the
* character sequence represented by this {@code String}
* object at an index no smaller than {@code fromIndex}, then
* the index of the first such occurrence is returned. For values
* of {@code ch} in the range from 0 to 0xFFFF (inclusive),
* this is the smallest value <i>k</i> such that:
* <blockquote><pre>
* (this.charAt(<i>k</i>) == ch) {@code &&} (<i>k</i> >= fromIndex)
* </pre></blockquote>
* is true. For other values of {@code ch}, it is the
* smallest value <i>k</i> such that:
* <blockquote><pre>
* (this.codePointAt(<i>k</i>) == ch) {@code &&} (<i>k</i> >= fromIndex)
* </pre></blockquote>
* is true. In either case, if no such character occurs in this
* string at or after position {@code fromIndex}, then
* {@code -1} is returned.
*
* <p>
* There is no restriction on the value of {@code fromIndex}. If it
* is negative, it has the same effect as if it were zero: this entire
* string may be searched. If it is greater than the length of this
* string, it has the same effect as if it were equal to the length of
* this string: {@code -1} is returned.
*
* <p>All indices are specified in {@code char} values
* (Unicode code units).
*
* @param ch a character (Unicode code point).
* @param fromIndex the index to start the search from.
* @return the index of the first occurrence of the character in the
* character sequence represented by this object that is greater
* than or equal to {@code fromIndex}, or {@code -1}
* if the character does not occur.
*/
public int
indexOf(int
ch, int
fromIndex) {
final int
max =
value.length;
if (
fromIndex < 0) {
fromIndex = 0;
} else if (
fromIndex >=
max) {
// Note: fromIndex might be near -1>>>1.
return -1;
}
if (
ch <
Character.
MIN_SUPPLEMENTARY_CODE_POINT) {
// handle most cases here (ch is a BMP code point or a
// negative value (invalid code point))
final char[]
value = this.
value;
for (int
i =
fromIndex;
i <
max;
i++) {
if (
value[
i] ==
ch) {
return
i;
}
}
return -1;
} else {
return
indexOfSupplementary(
ch,
fromIndex);
}
}
/**
* Handles (rare) calls of indexOf with a supplementary character.
*/
private int
indexOfSupplementary(int
ch, int
fromIndex) {
if (
Character.
isValidCodePoint(
ch)) {
final char[]
value = this.
value;
final char
hi =
Character.
highSurrogate(
ch);
final char
lo =
Character.
lowSurrogate(
ch);
final int
max =
value.length - 1;
for (int
i =
fromIndex;
i <
max;
i++) {
if (
value[
i] ==
hi &&
value[
i + 1] ==
lo) {
return
i;
}
}
}
return -1;
}
/**
* Returns the index within this string of the last occurrence of
* the specified character. For values of {@code ch} in the
* range from 0 to 0xFFFF (inclusive), the index (in Unicode code
* units) returned is the largest value <i>k</i> such that:
* <blockquote><pre>
* this.charAt(<i>k</i>) == ch
* </pre></blockquote>
* is true. For other values of {@code ch}, it is the
* largest value <i>k</i> such that:
* <blockquote><pre>
* this.codePointAt(<i>k</i>) == ch
* </pre></blockquote>
* is true. In either case, if no such character occurs in this
* string, then {@code -1} is returned. The
* {@code String} is searched backwards starting at the last
* character.
*
* @param ch a character (Unicode code point).
* @return the index of the last occurrence of the character in the
* character sequence represented by this object, or
* {@code -1} if the character does not occur.
*/
public int
lastIndexOf(int
ch) {
return
lastIndexOf(
ch,
value.length - 1);
}
/**
* Returns the index within this string of the last occurrence of
* the specified character, searching backward starting at the
* specified index. For values of {@code ch} in the range
* from 0 to 0xFFFF (inclusive), the index returned is the largest
* value <i>k</i> such that:
* <blockquote><pre>
* (this.charAt(<i>k</i>) == ch) {@code &&} (<i>k</i> <= fromIndex)
* </pre></blockquote>
* is true. For other values of {@code ch}, it is the
* largest value <i>k</i> such that:
* <blockquote><pre>
* (this.codePointAt(<i>k</i>) == ch) {@code &&} (<i>k</i> <= fromIndex)
* </pre></blockquote>
* is true. In either case, if no such character occurs in this
* string at or before position {@code fromIndex}, then
* {@code -1} is returned.
*
* <p>All indices are specified in {@code char} values
* (Unicode code units).
*
* @param ch a character (Unicode code point).
* @param fromIndex the index to start the search from. There is no
* restriction on the value of {@code fromIndex}. If it is
* greater than or equal to the length of this string, it has
* the same effect as if it were equal to one less than the
* length of this string: this entire string may be searched.
* If it is negative, it has the same effect as if it were -1:
* -1 is returned.
* @return the index of the last occurrence of the character in the
* character sequence represented by this object that is less
* than or equal to {@code fromIndex}, or {@code -1}
* if the character does not occur before that point.
*/
public int
lastIndexOf(int
ch, int
fromIndex) {
if (
ch <
Character.
MIN_SUPPLEMENTARY_CODE_POINT) {
// handle most cases here (ch is a BMP code point or a
// negative value (invalid code point))
final char[]
value = this.
value;
int
i =
Math.
min(
fromIndex,
value.length - 1);
for (;
i >= 0;
i--) {
if (
value[
i] ==
ch) {
return
i;
}
}
return -1;
} else {
return
lastIndexOfSupplementary(
ch,
fromIndex);
}
}
/**
* Handles (rare) calls of lastIndexOf with a supplementary character.
*/
private int
lastIndexOfSupplementary(int
ch, int
fromIndex) {
if (
Character.
isValidCodePoint(
ch)) {
final char[]
value = this.
value;
char
hi =
Character.
highSurrogate(
ch);
char
lo =
Character.
lowSurrogate(
ch);
int
i =
Math.
min(
fromIndex,
value.length - 2);
for (;
i >= 0;
i--) {
if (
value[
i] ==
hi &&
value[
i + 1] ==
lo) {
return
i;
}
}
}
return -1;
}
/**
* Returns the index within this string of the first occurrence of the
* specified substring.
*
* <p>The returned index is the smallest value <i>k</i> for which:
* <blockquote><pre>
* this.startsWith(str, <i>k</i>)
* </pre></blockquote>
* If no such value of <i>k</i> exists, then {@code -1} is returned.
*
* @param str the substring to search for.
* @return the index of the first occurrence of the specified substring,
* or {@code -1} if there is no such occurrence.
*/
public int
indexOf(
String str) {
return
indexOf(
str, 0);
}
/**
* Returns the index within this string of the first occurrence of the
* specified substring, starting at the specified index.
*
* <p>The returned index is the smallest value <i>k</i> for which:
* <blockquote><pre>
* <i>k</i> >= fromIndex {@code &&} this.startsWith(str, <i>k</i>)
* </pre></blockquote>
* If no such value of <i>k</i> exists, then {@code -1} is returned.
*
* @param str the substring to search for.
* @param fromIndex the index from which to start the search.
* @return the index of the first occurrence of the specified substring,
* starting at the specified index,
* or {@code -1} if there is no such occurrence.
*/
public int
indexOf(
String str, int
fromIndex) {
return
indexOf(
value, 0,
value.length,
str.
value, 0,
str.
value.length,
fromIndex);
}
/**
* Code shared by String and AbstractStringBuilder to do searches. The
* source is the character array being searched, and the target
* is the string being searched for.
*
* @param source the characters being searched.
* @param sourceOffset offset of the source string.
* @param sourceCount count of the source string.
* @param target the characters being searched for.
* @param fromIndex the index to begin searching from.
*/
static int
indexOf(char[]
source, int
sourceOffset, int
sourceCount,
String target, int
fromIndex) {
return
indexOf(
source,
sourceOffset,
sourceCount,
target.
value, 0,
target.
value.length,
fromIndex);
}
/**
* Code shared by String and StringBuffer to do searches. The
* source is the character array being searched, and the target
* is the string being searched for.
*
* @param source the characters being searched.
* @param sourceOffset offset of the source string.
* @param sourceCount count of the source string.
* @param target the characters being searched for.
* @param targetOffset offset of the target string.
* @param targetCount count of the target string.
* @param fromIndex the index to begin searching from.
*/
static int
indexOf(char[]
source, int
sourceOffset, int
sourceCount,
char[]
target, int
targetOffset, int
targetCount,
int
fromIndex) {
if (
fromIndex >=
sourceCount) {
return (
targetCount == 0 ?
sourceCount : -1);
}
if (
fromIndex < 0) {
fromIndex = 0;
}
if (
targetCount == 0) {
return
fromIndex;
}
char
first =
target[
targetOffset];
int
max =
sourceOffset + (
sourceCount -
targetCount);
for (int
i =
sourceOffset +
fromIndex;
i <=
max;
i++) {
/* Look for first character. */
if (
source[
i] !=
first) {
while (++
i <=
max &&
source[
i] !=
first);
}
/* Found first character, now look at the rest of v2 */
if (
i <=
max) {
int
j =
i + 1;
int
end =
j +
targetCount - 1;
for (int
k =
targetOffset + 1;
j <
end &&
source[
j]
==
target[
k];
j++,
k++);
if (
j ==
end) {
/* Found whole string. */
return
i -
sourceOffset;
}
}
}
return -1;
}
/**
* Returns the index within this string of the last occurrence of the
* specified substring. The last occurrence of the empty string ""
* is considered to occur at the index value {@code this.length()}.
*
* <p>The returned index is the largest value <i>k</i> for which:
* <blockquote><pre>
* this.startsWith(str, <i>k</i>)
* </pre></blockquote>
* If no such value of <i>k</i> exists, then {@code -1} is returned.
*
* @param str the substring to search for.
* @return the index of the last occurrence of the specified substring,
* or {@code -1} if there is no such occurrence.
*/
public int
lastIndexOf(
String str) {
return
lastIndexOf(
str,
value.length);
}
/**
* Returns the index within this string of the last occurrence of the
* specified substring, searching backward starting at the specified index.
*
* <p>The returned index is the largest value <i>k</i> for which:
* <blockquote><pre>
* <i>k</i> {@code <=} fromIndex {@code &&} this.startsWith(str, <i>k</i>)
* </pre></blockquote>
* If no such value of <i>k</i> exists, then {@code -1} is returned.
*
* @param str the substring to search for.
* @param fromIndex the index to start the search from.
* @return the index of the last occurrence of the specified substring,
* searching backward from the specified index,
* or {@code -1} if there is no such occurrence.
*/
public int
lastIndexOf(
String str, int
fromIndex) {
return
lastIndexOf(
value, 0,
value.length,
str.
value, 0,
str.
value.length,
fromIndex);
}
/**
* Code shared by String and AbstractStringBuilder to do searches. The
* source is the character array being searched, and the target
* is the string being searched for.
*
* @param source the characters being searched.
* @param sourceOffset offset of the source string.
* @param sourceCount count of the source string.
* @param target the characters being searched for.
* @param fromIndex the index to begin searching from.
*/
static int
lastIndexOf(char[]
source, int
sourceOffset, int
sourceCount,
String target, int
fromIndex) {
return
lastIndexOf(
source,
sourceOffset,
sourceCount,
target.
value, 0,
target.
value.length,
fromIndex);
}
/**
* Code shared by String and StringBuffer to do searches. The
* source is the character array being searched, and the target
* is the string being searched for.
*
* @param source the characters being searched.
* @param sourceOffset offset of the source string.
* @param sourceCount count of the source string.
* @param target the characters being searched for.
* @param targetOffset offset of the target string.
* @param targetCount count of the target string.
* @param fromIndex the index to begin searching from.
*/
static int
lastIndexOf(char[]
source, int
sourceOffset, int
sourceCount,
char[]
target, int
targetOffset, int
targetCount,
int
fromIndex) {
/*
* Check arguments; return immediately where possible. For
* consistency, don't check for null str.
*/
int
rightIndex =
sourceCount -
targetCount;
if (
fromIndex < 0) {
return -1;
}
if (
fromIndex >
rightIndex) {
fromIndex =
rightIndex;
}
/* Empty string always matches. */
if (
targetCount == 0) {
return
fromIndex;
}
int
strLastIndex =
targetOffset +
targetCount - 1;
char
strLastChar =
target[
strLastIndex];
int
min =
sourceOffset +
targetCount - 1;
int
i =
min +
fromIndex;
startSearchForLastChar:
while (true) {
while (
i >=
min &&
source[
i] !=
strLastChar) {
i--;
}
if (
i <
min) {
return -1;
}
int
j =
i - 1;
int
start =
j - (
targetCount - 1);
int
k =
strLastIndex - 1;
while (
j >
start) {
if (
source[
j--] !=
target[
k--]) {
i--;
continue
startSearchForLastChar;
}
}
return
start -
sourceOffset + 1;
}
}
/**
* Returns a string that is a substring of this string. The
* substring begins with the character at the specified index and
* extends to the end of this string. <p>
* Examples:
* <blockquote><pre>
* "unhappy".substring(2) returns "happy"
* "Harbison".substring(3) returns "bison"
* "emptiness".substring(9) returns "" (an empty string)
* </pre></blockquote>
*
* @param beginIndex the beginning index, inclusive.
* @return the specified substring.
* @exception IndexOutOfBoundsException if
* {@code beginIndex} is negative or larger than the
* length of this {@code String} object.
*/
public
String substring(int
beginIndex) {
if (
beginIndex < 0) {
throw new
StringIndexOutOfBoundsException(
beginIndex);
}
int
subLen =
value.length -
beginIndex;
if (
subLen < 0) {
throw new
StringIndexOutOfBoundsException(
subLen);
}
return (
beginIndex == 0) ? this : new
String(
value,
beginIndex,
subLen);
}
/**
* Returns a string that is a substring of this string. The
* substring begins at the specified {@code beginIndex} and
* extends to the character at index {@code endIndex - 1}.
* Thus the length of the substring is {@code endIndex-beginIndex}.
* <p>
* Examples:
* <blockquote><pre>
* "hamburger".substring(4, 8) returns "urge"
* "smiles".substring(1, 5) returns "mile"
* </pre></blockquote>
*
* @param beginIndex the beginning index, inclusive.
* @param endIndex the ending index, exclusive.
* @return the specified substring.
* @exception IndexOutOfBoundsException if the
* {@code beginIndex} is negative, or
* {@code endIndex} is larger than the length of
* this {@code String} object, or
* {@code beginIndex} is larger than
* {@code endIndex}.
*/
public
String substring(int
beginIndex, int
endIndex) {
if (
beginIndex < 0) {
throw new
StringIndexOutOfBoundsException(
beginIndex);
}
if (
endIndex >
value.length) {
throw new
StringIndexOutOfBoundsException(
endIndex);
}
int
subLen =
endIndex -
beginIndex;
if (
subLen < 0) {
throw new
StringIndexOutOfBoundsException(
subLen);
}
return ((
beginIndex == 0) && (
endIndex ==
value.length)) ? this
: new
String(
value,
beginIndex,
subLen);
}
/**
* Returns a character sequence that is a subsequence of this sequence.
*
* <p> An invocation of this method of the form
*
* <blockquote><pre>
* str.subSequence(begin, end)</pre></blockquote>
*
* behaves in exactly the same way as the invocation
*
* <blockquote><pre>
* str.substring(begin, end)</pre></blockquote>
*
* @apiNote
* This method is defined so that the {@code String} class can implement
* the {@link CharSequence} interface.
*
* @param beginIndex the begin index, inclusive.
* @param endIndex the end index, exclusive.
* @return the specified subsequence.
*
* @throws IndexOutOfBoundsException
* if {@code beginIndex} or {@code endIndex} is negative,
* if {@code endIndex} is greater than {@code length()},
* or if {@code beginIndex} is greater than {@code endIndex}
*
* @since 1.4
* @spec JSR-51
*/
public
CharSequence subSequence(int
beginIndex, int
endIndex) {
return this.
substring(
beginIndex,
endIndex);
}
/**
* Concatenates the specified string to the end of this string.
* <p>
* If the length of the argument string is {@code 0}, then this
* {@code String} object is returned. Otherwise, a
* {@code String} object is returned that represents a character
* sequence that is the concatenation of the character sequence
* represented by this {@code String} object and the character
* sequence represented by the argument string.<p>
* Examples:
* <blockquote><pre>
* "cares".concat("s") returns "caress"
* "to".concat("get").concat("her") returns "together"
* </pre></blockquote>
*
* @param str the {@code String} that is concatenated to the end
* of this {@code String}.
* @return a string that represents the concatenation of this object's
* characters followed by the string argument's characters.
*/
public
String concat(
String str) {
int
otherLen =
str.
length();
if (
otherLen == 0) {
return this;
}
int
len =
value.length;
char
buf[] =
Arrays.
copyOf(
value,
len +
otherLen);
str.
getChars(
buf,
len);
return new
String(
buf, true);
}
/**
* Returns a string resulting from replacing all occurrences of
* {@code oldChar} in this string with {@code newChar}.
* <p>
* If the character {@code oldChar} does not occur in the
* character sequence represented by this {@code String} object,
* then a reference to this {@code String} object is returned.
* Otherwise, a {@code String} object is returned that
* represents a character sequence identical to the character sequence
* represented by this {@code String} object, except that every
* occurrence of {@code oldChar} is replaced by an occurrence
* of {@code newChar}.
* <p>
* Examples:
* <blockquote><pre>
* "mesquite in your cellar".replace('e', 'o')
* returns "mosquito in your collar"
* "the war of baronets".replace('r', 'y')
* returns "the way of bayonets"
* "sparring with a purple porpoise".replace('p', 't')
* returns "starring with a turtle tortoise"
* "JonL".replace('q', 'x') returns "JonL" (no change)
* </pre></blockquote>
*
* @param oldChar the old character.
* @param newChar the new character.
* @return a string derived from this string by replacing every
* occurrence of {@code oldChar} with {@code newChar}.
*/
public
String replace(char
oldChar, char
newChar) {
if (
oldChar !=
newChar) {
int
len =
value.length;
int
i = -1;
char[]
val =
value; /* avoid getfield opcode */
while (++
i <
len) {
if (
val[
i] ==
oldChar) {
break;
}
}
if (
i <
len) {
char
buf[] = new char[
len];
for (int
j = 0;
j <
i;
j++) {
buf[
j] =
val[
j];
}
while (
i <
len) {
char
c =
val[
i];
buf[
i] = (
c ==
oldChar) ?
newChar :
c;
i++;
}
return new
String(
buf, true);
}
}
return this;
}
/**
* Tells whether or not this string matches the given <a
* href="../util/regex/Pattern.html#sum">regular expression</a>.
*
* <p> An invocation of this method of the form
* <i>str</i>{@code .matches(}<i>regex</i>{@code )} yields exactly the
* same result as the expression
*
* <blockquote>
* {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#matches(String,CharSequence)
* matches(<i>regex</i>, <i>str</i>)}
* </blockquote>
*
* @param regex
* the regular expression to which this string is to be matched
*
* @return {@code true} if, and only if, this string matches the
* given regular expression
*
* @throws PatternSyntaxException
* if the regular expression's syntax is invalid
*
* @see java.util.regex.Pattern
*
* @since 1.4
* @spec JSR-51
*/
public boolean
matches(
String regex) {
return
Pattern.
matches(
regex, this);
}
/**
* Returns true if and only if this string contains the specified
* sequence of char values.
*
* @param s the sequence to search for
* @return true if this string contains {@code s}, false otherwise
* @since 1.5
*/
public boolean
contains(
CharSequence s) {
return
indexOf(
s.
toString()) > -1;
}
/**
* Replaces the first substring of this string that matches the given <a
* href="../util/regex/Pattern.html#sum">regular expression</a> with the
* given replacement.
*
* <p> An invocation of this method of the form
* <i>str</i>{@code .replaceFirst(}<i>regex</i>{@code ,} <i>repl</i>{@code )}
* yields exactly the same result as the expression
*
* <blockquote>
* <code>
* {@link java.util.regex.Pattern}.{@link
* java.util.regex.Pattern#compile compile}(<i>regex</i>).{@link
* java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(<i>str</i>).{@link
* java.util.regex.Matcher#replaceFirst replaceFirst}(<i>repl</i>)
* </code>
* </blockquote>
*
*<p>
* Note that backslashes ({@code \}) and dollar signs ({@code $}) in the
* replacement string may cause the results to be different than if it were
* being treated as a literal replacement string; see
* {@link java.util.regex.Matcher#replaceFirst}.
* Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
* meaning of these characters, if desired.
*
* @param regex
* the regular expression to which this string is to be matched
* @param replacement
* the string to be substituted for the first match
*
* @return The resulting {@code String}
*
* @throws PatternSyntaxException
* if the regular expression's syntax is invalid
*
* @see java.util.regex.Pattern
*
* @since 1.4
* @spec JSR-51
*/
public
String replaceFirst(
String regex,
String replacement) {
return
Pattern.
compile(
regex).
matcher(this).
replaceFirst(
replacement);
}
/**
* Replaces each substring of this string that matches the given <a
* href="../util/regex/Pattern.html#sum">regular expression</a> with the
* given replacement.
*
* <p> An invocation of this method of the form
* <i>str</i>{@code .replaceAll(}<i>regex</i>{@code ,} <i>repl</i>{@code )}
* yields exactly the same result as the expression
*
* <blockquote>
* <code>
* {@link java.util.regex.Pattern}.{@link
* java.util.regex.Pattern#compile compile}(<i>regex</i>).{@link
* java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(<i>str</i>).{@link
* java.util.regex.Matcher#replaceAll replaceAll}(<i>repl</i>)
* </code>
* </blockquote>
*
*<p>
* Note that backslashes ({@code \}) and dollar signs ({@code $}) in the
* replacement string may cause the results to be different than if it were
* being treated as a literal replacement string; see
* {@link java.util.regex.Matcher#replaceAll Matcher.replaceAll}.
* Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
* meaning of these characters, if desired.
*
* @param regex
* the regular expression to which this string is to be matched
* @param replacement
* the string to be substituted for each match
*
* @return The resulting {@code String}
*
* @throws PatternSyntaxException
* if the regular expression's syntax is invalid
*
* @see java.util.regex.Pattern
*
* @since 1.4
* @spec JSR-51
*/
public
String replaceAll(
String regex,
String replacement) {
return
Pattern.
compile(
regex).
matcher(this).
replaceAll(
replacement);
}
/**
* Replaces each substring of this string that matches the literal target
* sequence with the specified literal replacement sequence. The
* replacement proceeds from the beginning of the string to the end, for
* example, replacing "aa" with "b" in the string "aaa" will result in
* "ba" rather than "ab".
*
* @param target The sequence of char values to be replaced
* @param replacement The replacement sequence of char values
* @return The resulting string
* @since 1.5
*/
public
String replace(
CharSequence target,
CharSequence replacement) {
return
Pattern.
compile(
target.
toString(),
Pattern.
LITERAL).
matcher(
this).
replaceAll(
Matcher.
quoteReplacement(
replacement.
toString()));
}
/**
* Splits this string around matches of the given
* <a href="../util/regex/Pattern.html#sum">regular expression</a>.
*
* <p> The array returned by this method contains each substring of this
* string that is terminated by another substring that matches the given
* expression or is terminated by the end of the string. The substrings in
* the array are in the order in which they occur in this string. If the
* expression does not match any part of the input then the resulting array
* has just one element, namely this string.
*
* <p> When there is a positive-width match at the beginning of this
* string then an empty leading substring is included at the beginning
* of the resulting array. A zero-width match at the beginning however
* never produces such empty leading substring.
*
* <p> The {@code limit} parameter controls the number of times the
* pattern is applied and therefore affects the length of the resulting
* array. If the limit <i>n</i> is greater than zero then the pattern
* will be applied at most <i>n</i> - 1 times, the array's
* length will be no greater than <i>n</i>, and the array's last entry
* will contain all input beyond the last matched delimiter. If <i>n</i>
* is non-positive then the pattern will be applied as many times as
* possible and the array can have any length. If <i>n</i> is zero then
* the pattern will be applied as many times as possible, the array can
* have any length, and trailing empty strings will be discarded.
*
* <p> The string {@code "boo:and:foo"}, for example, yields the
* following results with these parameters:
*
* <blockquote><table cellpadding=1 cellspacing=0 summary="Split example showing regex, limit, and result">
* <tr>
* <th>Regex</th>
* <th>Limit</th>
* <th>Result</th>
* </tr>
* <tr><td align=center>:</td>
* <td align=center>2</td>
* <td>{@code { "boo", "and:foo" }}</td></tr>
* <tr><td align=center>:</td>
* <td align=center>5</td>
* <td>{@code { "boo", "and", "foo" }}</td></tr>
* <tr><td align=center>:</td>
* <td align=center>-2</td>
* <td>{@code { "boo", "and", "foo" }}</td></tr>
* <tr><td align=center>o</td>
* <td align=center>5</td>
* <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
* <tr><td align=center>o</td>
* <td align=center>-2</td>
* <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
* <tr><td align=center>o</td>
* <td align=center>0</td>
* <td>{@code { "b", "", ":and:f" }}</td></tr>
* </table></blockquote>
*
* <p> An invocation of this method of the form
* <i>str.</i>{@code split(}<i>regex</i>{@code ,} <i>n</i>{@code )}
* yields the same result as the expression
*
* <blockquote>
* <code>
* {@link java.util.regex.Pattern}.{@link
* java.util.regex.Pattern#compile compile}(<i>regex</i>).{@link
* java.util.regex.Pattern#split(java.lang.CharSequence,int) split}(<i>str</i>, <i>n</i>)
* </code>
* </blockquote>
*
*
* @param regex
* the delimiting regular expression
*
* @param limit
* the result threshold, as described above
*
* @return the array of strings computed by splitting this string
* around matches of the given regular expression
*
* @throws PatternSyntaxException
* if the regular expression's syntax is invalid
*
* @see java.util.regex.Pattern
*
* @since 1.4
* @spec JSR-51
*/
public
String[]
split(
String regex, int
limit) {
/* fastpath if the regex is a
(1)one-char String and this character is not one of the
RegEx's meta characters ".$|()[{^?*+\\", or
(2)two-char String and the first char is the backslash and
the second is not the ascii digit or ascii letter.
*/
char
ch = 0;
if (((
regex.
value.length == 1 &&
".$|()[{^?*+\\".
indexOf(
ch =
regex.
charAt(0)) == -1) ||
(
regex.
length() == 2 &&
regex.
charAt(0) == '\\' &&
(((
ch =
regex.
charAt(1))-'0')|('9'-
ch)) < 0 &&
((
ch-'a')|('z'-
ch)) < 0 &&
((
ch-'A')|('Z'-
ch)) < 0)) &&
(
ch <
Character.
MIN_HIGH_SURROGATE ||
ch >
Character.
MAX_LOW_SURROGATE))
{
int
off = 0;
int
next = 0;
boolean
limited =
limit > 0;
ArrayList<
String>
list = new
ArrayList<>();
while ((
next =
indexOf(
ch,
off)) != -1) {
if (!
limited ||
list.
size() <
limit - 1) {
list.
add(
substring(
off,
next));
off =
next + 1;
} else { // last one
//assert (list.size() == limit - 1);
list.
add(
substring(
off,
value.length));
off =
value.length;
break;
}
}
// If no match was found, return this
if (
off == 0)
return new
String[]{this};
// Add remaining segment
if (!
limited ||
list.
size() <
limit)
list.
add(
substring(
off,
value.length));
// Construct result
int
resultSize =
list.
size();
if (
limit == 0) {
while (
resultSize > 0 &&
list.
get(
resultSize - 1).
length() == 0) {
resultSize--;
}
}
String[]
result = new
String[
resultSize];
return
list.
subList(0,
resultSize).
toArray(
result);
}
return
Pattern.
compile(
regex).
split(this,
limit);
}
/**
* Splits this string around matches of the given <a
* href="../util/regex/Pattern.html#sum">regular expression</a>.
*
* <p> This method works as if by invoking the two-argument {@link
* #split(String, int) split} method with the given expression and a limit
* argument of zero. Trailing empty strings are therefore not included in
* the resulting array.
*
* <p> The string {@code "boo:and:foo"}, for example, yields the following
* results with these expressions:
*
* <blockquote><table cellpadding=1 cellspacing=0 summary="Split examples showing regex and result">
* <tr>
* <th>Regex</th>
* <th>Result</th>
* </tr>
* <tr><td align=center>:</td>
* <td>{@code { "boo", "and", "foo" }}</td></tr>
* <tr><td align=center>o</td>
* <td>{@code { "b", "", ":and:f" }}</td></tr>
* </table></blockquote>
*
*
* @param regex
* the delimiting regular expression
*
* @return the array of strings computed by splitting this string
* around matches of the given regular expression
*
* @throws PatternSyntaxException
* if the regular expression's syntax is invalid
*
* @see java.util.regex.Pattern
*
* @since 1.4
* @spec JSR-51
*/
public
String[]
split(
String regex) {
return
split(
regex, 0);
}
/**
* Returns a new String composed of copies of the
* {@code CharSequence elements} joined together with a copy of
* the specified {@code delimiter}.
*
* <blockquote>For example,
* <pre>{@code
* String message = String.join("-", "Java", "is", "cool");
* // message returned is: "Java-is-cool"
* }</pre></blockquote>
*
* Note that if an element is null, then {@code "null"} is added.
*
* @param delimiter the delimiter that separates each element
* @param elements the elements to join together.
*
* @return a new {@code String} that is composed of the {@code elements}
* separated by the {@code delimiter}
*
* @throws NullPointerException If {@code delimiter} or {@code elements}
* is {@code null}
*
* @see java.util.StringJoiner
* @since 1.8
*/
public static
String join(
CharSequence delimiter,
CharSequence...
elements) {
Objects.
requireNonNull(
delimiter);
Objects.
requireNonNull(
elements);
// Number of elements not likely worth Arrays.stream overhead.
StringJoiner joiner = new
StringJoiner(
delimiter);
for (
CharSequence cs:
elements) {
joiner.
add(
cs);
}
return
joiner.
toString();
}
/**
* Returns a new {@code String} composed of copies of the
* {@code CharSequence elements} joined together with a copy of the
* specified {@code delimiter}.
*
* <blockquote>For example,
* <pre>{@code
* List<String> strings = new LinkedList<>();
* strings.add("Java");strings.add("is");
* strings.add("cool");
* String message = String.join(" ", strings);
* //message returned is: "Java is cool"
*
* Set<String> strings = new LinkedHashSet<>();
* strings.add("Java"); strings.add("is");
* strings.add("very"); strings.add("cool");
* String message = String.join("-", strings);
* //message returned is: "Java-is-very-cool"
* }</pre></blockquote>
*
* Note that if an individual element is {@code null}, then {@code "null"} is added.
*
* @param delimiter a sequence of characters that is used to separate each
* of the {@code elements} in the resulting {@code String}
* @param elements an {@code Iterable} that will have its {@code elements}
* joined together.
*
* @return a new {@code String} that is composed from the {@code elements}
* argument
*
* @throws NullPointerException If {@code delimiter} or {@code elements}
* is {@code null}
*
* @see #join(CharSequence,CharSequence...)
* @see java.util.StringJoiner
* @since 1.8
*/
public static
String join(
CharSequence delimiter,
Iterable<? extends
CharSequence>
elements) {
Objects.
requireNonNull(
delimiter);
Objects.
requireNonNull(
elements);
StringJoiner joiner = new
StringJoiner(
delimiter);
for (
CharSequence cs:
elements) {
joiner.
add(
cs);
}
return
joiner.
toString();
}
/**
* Converts all of the characters in this {@code String} to lower
* case using the rules of the given {@code Locale}. Case mapping is based
* on the Unicode Standard version specified by the {@link java.lang.Character Character}
* class. Since case mappings are not always 1:1 char mappings, the resulting
* {@code String} may be a different length than the original {@code String}.
* <p>
* Examples of lowercase mappings are in the following table:
* <table border="1" summary="Lowercase mapping examples showing language code of locale, upper case, lower case, and description">
* <tr>
* <th>Language Code of Locale</th>
* <th>Upper Case</th>
* <th>Lower Case</th>
* <th>Description</th>
* </tr>
* <tr>
* <td>tr (Turkish)</td>
* <td>\u0130</td>
* <td>\u0069</td>
* <td>capital letter I with dot above -> small letter i</td>
* </tr>
* <tr>
* <td>tr (Turkish)</td>
* <td>\u0049</td>
* <td>\u0131</td>
* <td>capital letter I -> small letter dotless i </td>
* </tr>
* <tr>
* <td>(all)</td>
* <td>French Fries</td>
* <td>french fries</td>
* <td>lowercased all chars in String</td>
* </tr>
* <tr>
* <td>(all)</td>
* <td><img src="doc-files/capiota.gif" alt="capiota"><img src="doc-files/capchi.gif" alt="capchi">
* <img src="doc-files/captheta.gif" alt="captheta"><img src="doc-files/capupsil.gif" alt="capupsil">
* <img src="doc-files/capsigma.gif" alt="capsigma"></td>
* <td><img src="doc-files/iota.gif" alt="iota"><img src="doc-files/chi.gif" alt="chi">
* <img src="doc-files/theta.gif" alt="theta"><img src="doc-files/upsilon.gif" alt="upsilon">
* <img src="doc-files/sigma1.gif" alt="sigma"></td>
* <td>lowercased all chars in String</td>
* </tr>
* </table>
*
* @param locale use the case transformation rules for this locale
* @return the {@code String}, converted to lowercase.
* @see java.lang.String#toLowerCase()
* @see java.lang.String#toUpperCase()
* @see java.lang.String#toUpperCase(Locale)
* @since 1.1
*/
public
String toLowerCase(
Locale locale) {
if (
locale == null) {
throw new
NullPointerException();
}
int
firstUpper;
final int
len =
value.length;
/* Now check if there are any characters that need to be changed. */
scan: {
for (
firstUpper = 0 ;
firstUpper <
len; ) {
char
c =
value[
firstUpper];
if ((
c >=
Character.
MIN_HIGH_SURROGATE)
&& (
c <=
Character.
MAX_HIGH_SURROGATE)) {
int
supplChar =
codePointAt(
firstUpper);
if (
supplChar !=
Character.
toLowerCase(
supplChar)) {
break
scan;
}
firstUpper +=
Character.
charCount(
supplChar);
} else {
if (
c !=
Character.
toLowerCase(
c)) {
break
scan;
}
firstUpper++;
}
}
return this;
}
char[]
result = new char[
len];
int
resultOffset = 0; /* result may grow, so i+resultOffset
* is the write location in result */
/* Just copy the first few lowerCase characters. */
System.
arraycopy(
value, 0,
result, 0,
firstUpper);
String lang =
locale.
getLanguage();
boolean
localeDependent =
(
lang == "tr" ||
lang == "az" ||
lang == "lt");
char[]
lowerCharArray;
int
lowerChar;
int
srcChar;
int
srcCount;
for (int
i =
firstUpper;
i <
len;
i +=
srcCount) {
srcChar = (int)
value[
i];
if ((char)
srcChar >=
Character.
MIN_HIGH_SURROGATE
&& (char)
srcChar <=
Character.
MAX_HIGH_SURROGATE) {
srcChar =
codePointAt(
i);
srcCount =
Character.
charCount(
srcChar);
} else {
srcCount = 1;
}
if (
localeDependent ||
srcChar == '\u03A3' || // GREEK CAPITAL LETTER SIGMA
srcChar == '\u0130') { // LATIN CAPITAL LETTER I WITH DOT ABOVE
lowerChar =
ConditionalSpecialCasing.
toLowerCaseEx(this,
i,
locale);
} else {
lowerChar =
Character.
toLowerCase(
srcChar);
}
if ((
lowerChar ==
Character.
ERROR)
|| (
lowerChar >=
Character.
MIN_SUPPLEMENTARY_CODE_POINT)) {
if (
lowerChar ==
Character.
ERROR) {
lowerCharArray =
ConditionalSpecialCasing.
toLowerCaseCharArray(this,
i,
locale);
} else if (
srcCount == 2) {
resultOffset +=
Character.
toChars(
lowerChar,
result,
i +
resultOffset) -
srcCount;
continue;
} else {
lowerCharArray =
Character.
toChars(
lowerChar);
}
/* Grow result if needed */
int
mapLen =
lowerCharArray.length;
if (
mapLen >
srcCount) {
char[]
result2 = new char[
result.length +
mapLen -
srcCount];
System.
arraycopy(
result, 0,
result2, 0,
i +
resultOffset);
result =
result2;
}
for (int
x = 0;
x <
mapLen; ++
x) {
result[
i +
resultOffset +
x] =
lowerCharArray[
x];
}
resultOffset += (
mapLen -
srcCount);
} else {
result[
i +
resultOffset] = (char)
lowerChar;
}
}
return new
String(
result, 0,
len +
resultOffset);
}
/**
* Converts all of the characters in this {@code String} to lower
* case using the rules of the default locale. This is equivalent to calling
* {@code toLowerCase(Locale.getDefault())}.
* <p>
* <b>Note:</b> This method is locale sensitive, and may produce unexpected
* results if used for strings that are intended to be interpreted locale
* independently.
* Examples are programming language identifiers, protocol keys, and HTML
* tags.
* For instance, {@code "TITLE".toLowerCase()} in a Turkish locale
* returns {@code "t\u005Cu0131tle"}, where '\u005Cu0131' is the
* LATIN SMALL LETTER DOTLESS I character.
* To obtain correct results for locale insensitive strings, use
* {@code toLowerCase(Locale.ROOT)}.
* <p>
* @return the {@code String}, converted to lowercase.
* @see java.lang.String#toLowerCase(Locale)
*/
public
String toLowerCase() {
return
toLowerCase(
Locale.
getDefault());
}
/**
* Converts all of the characters in this {@code String} to upper
* case using the rules of the given {@code Locale}. Case mapping is based
* on the Unicode Standard version specified by the {@link java.lang.Character Character}
* class. Since case mappings are not always 1:1 char mappings, the resulting
* {@code String} may be a different length than the original {@code String}.
* <p>
* Examples of locale-sensitive and 1:M case mappings are in the following table.
*
* <table border="1" summary="Examples of locale-sensitive and 1:M case mappings. Shows Language code of locale, lower case, upper case, and description.">
* <tr>
* <th>Language Code of Locale</th>
* <th>Lower Case</th>
* <th>Upper Case</th>
* <th>Description</th>
* </tr>
* <tr>
* <td>tr (Turkish)</td>
* <td>\u0069</td>
* <td>\u0130</td>
* <td>small letter i -> capital letter I with dot above</td>
* </tr>
* <tr>
* <td>tr (Turkish)</td>
* <td>\u0131</td>
* <td>\u0049</td>
* <td>small letter dotless i -> capital letter I</td>
* </tr>
* <tr>
* <td>(all)</td>
* <td>\u00df</td>
* <td>\u0053 \u0053</td>
* <td>small letter sharp s -> two letters: SS</td>
* </tr>
* <tr>
* <td>(all)</td>
* <td>Fahrvergnügen</td>
* <td>FAHRVERGNÜGEN</td>
* <td></td>
* </tr>
* </table>
* @param locale use the case transformation rules for this locale
* @return the {@code String}, converted to uppercase.
* @see java.lang.String#toUpperCase()
* @see java.lang.String#toLowerCase()
* @see java.lang.String#toLowerCase(Locale)
* @since 1.1
*/
public
String toUpperCase(
Locale locale) {
if (
locale == null) {
throw new
NullPointerException();
}
int
firstLower;
final int
len =
value.length;
/* Now check if there are any characters that need to be changed. */
scan: {
for (
firstLower = 0 ;
firstLower <
len; ) {
int
c = (int)
value[
firstLower];
int
srcCount;
if ((
c >=
Character.
MIN_HIGH_SURROGATE)
&& (
c <=
Character.
MAX_HIGH_SURROGATE)) {
c =
codePointAt(
firstLower);
srcCount =
Character.
charCount(
c);
} else {
srcCount = 1;
}
int
upperCaseChar =
Character.
toUpperCaseEx(
c);
if ((
upperCaseChar ==
Character.
ERROR)
|| (
c !=
upperCaseChar)) {
break
scan;
}
firstLower +=
srcCount;
}
return this;
}
/* result may grow, so i+resultOffset is the write location in result */
int
resultOffset = 0;
char[]
result = new char[
len]; /* may grow */
/* Just copy the first few upperCase characters. */
System.
arraycopy(
value, 0,
result, 0,
firstLower);
String lang =
locale.
getLanguage();
boolean
localeDependent =
(
lang == "tr" ||
lang == "az" ||
lang == "lt");
char[]
upperCharArray;
int
upperChar;
int
srcChar;
int
srcCount;
for (int
i =
firstLower;
i <
len;
i +=
srcCount) {
srcChar = (int)
value[
i];
if ((char)
srcChar >=
Character.
MIN_HIGH_SURROGATE &&
(char)
srcChar <=
Character.
MAX_HIGH_SURROGATE) {
srcChar =
codePointAt(
i);
srcCount =
Character.
charCount(
srcChar);
} else {
srcCount = 1;
}
if (
localeDependent) {
upperChar =
ConditionalSpecialCasing.
toUpperCaseEx(this,
i,
locale);
} else {
upperChar =
Character.
toUpperCaseEx(
srcChar);
}
if ((
upperChar ==
Character.
ERROR)
|| (
upperChar >=
Character.
MIN_SUPPLEMENTARY_CODE_POINT)) {
if (
upperChar ==
Character.
ERROR) {
if (
localeDependent) {
upperCharArray =
ConditionalSpecialCasing.
toUpperCaseCharArray(this,
i,
locale);
} else {
upperCharArray =
Character.
toUpperCaseCharArray(
srcChar);
}
} else if (
srcCount == 2) {
resultOffset +=
Character.
toChars(
upperChar,
result,
i +
resultOffset) -
srcCount;
continue;
} else {
upperCharArray =
Character.
toChars(
upperChar);
}
/* Grow result if needed */
int
mapLen =
upperCharArray.length;
if (
mapLen >
srcCount) {
char[]
result2 = new char[
result.length +
mapLen -
srcCount];
System.
arraycopy(
result, 0,
result2, 0,
i +
resultOffset);
result =
result2;
}
for (int
x = 0;
x <
mapLen; ++
x) {
result[
i +
resultOffset +
x] =
upperCharArray[
x];
}
resultOffset += (
mapLen -
srcCount);
} else {
result[
i +
resultOffset] = (char)
upperChar;
}
}
return new
String(
result, 0,
len +
resultOffset);
}
/**
* Converts all of the characters in this {@code String} to upper
* case using the rules of the default locale. This method is equivalent to
* {@code toUpperCase(Locale.getDefault())}.
* <p>
* <b>Note:</b> This method is locale sensitive, and may produce unexpected
* results if used for strings that are intended to be interpreted locale
* independently.
* Examples are programming language identifiers, protocol keys, and HTML
* tags.
* For instance, {@code "title".toUpperCase()} in a Turkish locale
* returns {@code "T\u005Cu0130TLE"}, where '\u005Cu0130' is the
* LATIN CAPITAL LETTER I WITH DOT ABOVE character.
* To obtain correct results for locale insensitive strings, use
* {@code toUpperCase(Locale.ROOT)}.
* <p>
* @return the {@code String}, converted to uppercase.
* @see java.lang.String#toUpperCase(Locale)
*/
public
String toUpperCase() {
return
toUpperCase(
Locale.
getDefault());
}
/**
* Returns a string whose value is this string, with any leading and trailing
* whitespace removed.
* <p>
* If this {@code String} object represents an empty character
* sequence, or the first and last characters of character sequence
* represented by this {@code String} object both have codes
* greater than {@code '\u005Cu0020'} (the space character), then a
* reference to this {@code String} object is returned.
* <p>
* Otherwise, if there is no character with a code greater than
* {@code '\u005Cu0020'} in the string, then a
* {@code String} object representing an empty string is
* returned.
* <p>
* Otherwise, let <i>k</i> be the index of the first character in the
* string whose code is greater than {@code '\u005Cu0020'}, and let
* <i>m</i> be the index of the last character in the string whose code
* is greater than {@code '\u005Cu0020'}. A {@code String}
* object is returned, representing the substring of this string that
* begins with the character at index <i>k</i> and ends with the
* character at index <i>m</i>-that is, the result of
* {@code this.substring(k, m + 1)}.
* <p>
* This method may be used to trim whitespace (as defined above) from
* the beginning and end of a string.
*
* @return A string whose value is this string, with any leading and trailing white
* space removed, or this string if it has no leading or
* trailing white space.
*/
public
String trim() {
int
len =
value.length;
int
st = 0;
char[]
val =
value; /* avoid getfield opcode */
while ((
st <
len) && (
val[
st] <= ' ')) {
st++;
}
while ((
st <
len) && (
val[
len - 1] <= ' ')) {
len--;
}
return ((
st > 0) || (
len <
value.length)) ?
substring(
st,
len) : this;
}
/**
* This object (which is already a string!) is itself returned.
*
* @return the string itself.
*/
public
String toString() {
return this;
}
/**
* Converts this string to a new character array.
*
* @return a newly allocated character array whose length is the length
* of this string and whose contents are initialized to contain
* the character sequence represented by this string.
*/
public char[]
toCharArray() {
// Cannot use Arrays.copyOf because of class initialization order issues
char
result[] = new char[
value.length];
System.
arraycopy(
value, 0,
result, 0,
value.length);
return
result;
}
/**
* Returns a formatted string using the specified format string and
* arguments.
*
* <p> The locale always used is the one returned by {@link
* java.util.Locale#getDefault() Locale.getDefault()}.
*
* @param format
* A <a href="../util/Formatter.html#syntax">format string</a>
*
* @param args
* Arguments referenced by the format specifiers in the format
* string. If there are more arguments than format specifiers, the
* extra arguments are ignored. The number of arguments is
* variable and may be zero. The maximum number of arguments is
* limited by the maximum dimension of a Java array as defined by
* <cite>The Java™ Virtual Machine Specification</cite>.
* The behaviour on a
* {@code null} argument depends on the <a
* href="../util/Formatter.html#syntax">conversion</a>.
*
* @throws java.util.IllegalFormatException
* If a format string contains an illegal syntax, a format
* specifier that is incompatible with the given arguments,
* insufficient arguments given the format string, or other
* illegal conditions. For specification of all possible
* formatting errors, see the <a
* href="../util/Formatter.html#detail">Details</a> section of the
* formatter class specification.
*
* @return A formatted string
*
* @see java.util.Formatter
* @since 1.5
*/
public static
String format(
String format,
Object...
args) {
return new
Formatter().
format(
format,
args).
toString();
}
/**
* Returns a formatted string using the specified locale, format string,
* and arguments.
*
* @param l
* The {@linkplain java.util.Locale locale} to apply during
* formatting. If {@code l} is {@code null} then no localization
* is applied.
*
* @param format
* A <a href="../util/Formatter.html#syntax">format string</a>
*
* @param args
* Arguments referenced by the format specifiers in the format
* string. If there are more arguments than format specifiers, the
* extra arguments are ignored. The number of arguments is
* variable and may be zero. The maximum number of arguments is
* limited by the maximum dimension of a Java array as defined by
* <cite>The Java™ Virtual Machine Specification</cite>.
* The behaviour on a
* {@code null} argument depends on the
* <a href="../util/Formatter.html#syntax">conversion</a>.
*
* @throws java.util.IllegalFormatException
* If a format string contains an illegal syntax, a format
* specifier that is incompatible with the given arguments,
* insufficient arguments given the format string, or other
* illegal conditions. For specification of all possible
* formatting errors, see the <a
* href="../util/Formatter.html#detail">Details</a> section of the
* formatter class specification
*
* @return A formatted string
*
* @see java.util.Formatter
* @since 1.5
*/
public static
String format(
Locale l,
String format,
Object...
args) {
return new
Formatter(
l).
format(
format,
args).
toString();
}
/**
* Returns the string representation of the {@code Object} argument.
*
* @param obj an {@code Object}.
* @return if the argument is {@code null}, then a string equal to
* {@code "null"}; otherwise, the value of
* {@code obj.toString()} is returned.
* @see java.lang.Object#toString()
*/
public static
String valueOf(
Object obj) {
return (
obj == null) ? "null" :
obj.
toString();
}
/**
* Returns the string representation of the {@code char} array
* argument. The contents of the character array are copied; subsequent
* modification of the character array does not affect the returned
* string.
*
* @param data the character array.
* @return a {@code String} that contains the characters of the
* character array.
*/
public static
String valueOf(char
data[]) {
return new
String(
data);
}
/**
* Returns the string representation of a specific subarray of the
* {@code char} array argument.
* <p>
* The {@code offset} argument is the index of the first
* character of the subarray. The {@code count} argument
* specifies the length of the subarray. The contents of the subarray
* are copied; subsequent modification of the character array does not
* affect the returned string.
*
* @param data the character array.
* @param offset initial offset of the subarray.
* @param count length of the subarray.
* @return a {@code String} that contains the characters of the
* specified subarray of the character array.
* @exception IndexOutOfBoundsException if {@code offset} is
* negative, or {@code count} is negative, or
* {@code offset+count} is larger than
* {@code data.length}.
*/
public static
String valueOf(char
data[], int
offset, int
count) {
return new
String(
data,
offset,
count);
}
/**
* Equivalent to {@link #valueOf(char[], int, int)}.
*
* @param data the character array.
* @param offset initial offset of the subarray.
* @param count length of the subarray.
* @return a {@code String} that contains the characters of the
* specified subarray of the character array.
* @exception IndexOutOfBoundsException if {@code offset} is
* negative, or {@code count} is negative, or
* {@code offset+count} is larger than
* {@code data.length}.
*/
public static
String copyValueOf(char
data[], int
offset, int
count) {
return new
String(
data,
offset,
count);
}
/**
* Equivalent to {@link #valueOf(char[])}.
*
* @param data the character array.
* @return a {@code String} that contains the characters of the
* character array.
*/
public static
String copyValueOf(char
data[]) {
return new
String(
data);
}
/**
* Returns the string representation of the {@code boolean} argument.
*
* @param b a {@code boolean}.
* @return if the argument is {@code true}, a string equal to
* {@code "true"} is returned; otherwise, a string equal to
* {@code "false"} is returned.
*/
public static
String valueOf(boolean
b) {
return
b ? "true" : "false";
}
/**
* Returns the string representation of the {@code char}
* argument.
*
* @param c a {@code char}.
* @return a string of length {@code 1} containing
* as its single character the argument {@code c}.
*/
public static
String valueOf(char
c) {
char
data[] = {
c};
return new
String(
data, true);
}
/**
* Returns the string representation of the {@code int} argument.
* <p>
* The representation is exactly the one returned by the
* {@code Integer.toString} method of one argument.
*
* @param i an {@code int}.
* @return a string representation of the {@code int} argument.
* @see java.lang.Integer#toString(int, int)
*/
public static
String valueOf(int
i) {
return
Integer.
toString(
i);
}
/**
* Returns the string representation of the {@code long} argument.
* <p>
* The representation is exactly the one returned by the
* {@code Long.toString} method of one argument.
*
* @param l a {@code long}.
* @return a string representation of the {@code long} argument.
* @see java.lang.Long#toString(long)
*/
public static
String valueOf(long
l) {
return
Long.
toString(
l);
}
/**
* Returns the string representation of the {@code float} argument.
* <p>
* The representation is exactly the one returned by the
* {@code Float.toString} method of one argument.
*
* @param f a {@code float}.
* @return a string representation of the {@code float} argument.
* @see java.lang.Float#toString(float)
*/
public static
String valueOf(float
f) {
return
Float.
toString(
f);
}
/**
* Returns the string representation of the {@code double} argument.
* <p>
* The representation is exactly the one returned by the
* {@code Double.toString} method of one argument.
*
* @param d a {@code double}.
* @return a string representation of the {@code double} argument.
* @see java.lang.Double#toString(double)
*/
public static
String valueOf(double
d) {
return
Double.
toString(
d);
}
/**
* Returns a canonical representation for the string object.
* <p>
* A pool of strings, initially empty, is maintained privately by the
* class {@code String}.
* <p>
* When the intern method is invoked, if the pool already contains a
* string equal to this {@code String} object as determined by
* the {@link #equals(Object)} method, then the string from the pool is
* returned. Otherwise, this {@code String} object is added to the
* pool and a reference to this {@code String} object is returned.
* <p>
* It follows that for any two strings {@code s} and {@code t},
* {@code s.intern() == t.intern()} is {@code true}
* if and only if {@code s.equals(t)} is {@code true}.
* <p>
* All literal strings and string-valued constant expressions are
* interned. String literals are defined in section 3.10.5 of the
* <cite>The Java™ Language Specification</cite>.
*
* @return a string that has the same contents as this string, but is
* guaranteed to be from a pool of unique strings.
*/
public native
String intern();
}