/*
* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package java.lang;
import java.util.
Objects;
/**
* An element in a stack trace, as returned by {@link
* Throwable#getStackTrace()}. Each element represents a single stack frame.
* All stack frames except for the one at the top of the stack represent
* a method invocation. The frame at the top of the stack represents the
* execution point at which the stack trace was generated. Typically,
* this is the point at which the throwable corresponding to the stack trace
* was created.
*
* @since 1.4
* @author Josh Bloch
*/
public final class
StackTraceElement implements java.io.
Serializable {
// Normally initialized by VM (public constructor added in 1.5)
private
String declaringClass;
private
String methodName;
private
String fileName;
private int
lineNumber;
/**
* Creates a stack trace element representing the specified execution
* point.
*
* @param declaringClass the fully qualified name of the class containing
* the execution point represented by the stack trace element
* @param methodName the name of the method containing the execution point
* represented by the stack trace element
* @param fileName the name of the file containing the execution point
* represented by the stack trace element, or {@code null} if
* this information is unavailable
* @param lineNumber the line number of the source line containing the
* execution point represented by this stack trace element, or
* a negative number if this information is unavailable. A value
* of -2 indicates that the method containing the execution point
* is a native method
* @throws NullPointerException if {@code declaringClass} or
* {@code methodName} is null
* @since 1.5
*/
public
StackTraceElement(
String declaringClass,
String methodName,
String fileName, int
lineNumber) {
this.
declaringClass =
Objects.
requireNonNull(
declaringClass, "Declaring class is null");
this.
methodName =
Objects.
requireNonNull(
methodName, "Method name is null");
this.
fileName =
fileName;
this.
lineNumber =
lineNumber;
}
/**
* Returns the name of the source file containing the execution point
* represented by this stack trace element. Generally, this corresponds
* to the {@code SourceFile} attribute of the relevant {@code class}
* file (as per <i>The Java Virtual Machine Specification</i>, Section
* 4.7.7). In some systems, the name may refer to some source code unit
* other than a file, such as an entry in source repository.
*
* @return the name of the file containing the execution point
* represented by this stack trace element, or {@code null} if
* this information is unavailable.
*/
public
String getFileName() {
return
fileName;
}
/**
* Returns the line number of the source line containing the execution
* point represented by this stack trace element. Generally, this is
* derived from the {@code LineNumberTable} attribute of the relevant
* {@code class} file (as per <i>The Java Virtual Machine
* Specification</i>, Section 4.7.8).
*
* @return the line number of the source line containing the execution
* point represented by this stack trace element, or a negative
* number if this information is unavailable.
*/
public int
getLineNumber() {
return
lineNumber;
}
/**
* Returns the fully qualified name of the class containing the
* execution point represented by this stack trace element.
*
* @return the fully qualified name of the {@code Class} containing
* the execution point represented by this stack trace element.
*/
public
String getClassName() {
return
declaringClass;
}
/**
* Returns the name of the method containing the execution point
* represented by this stack trace element. If the execution point is
* contained in an instance or class initializer, this method will return
* the appropriate <i>special method name</i>, {@code <init>} or
* {@code <clinit>}, as per Section 3.9 of <i>The Java Virtual
* Machine Specification</i>.
*
* @return the name of the method containing the execution point
* represented by this stack trace element.
*/
public
String getMethodName() {
return
methodName;
}
/**
* Returns true if the method containing the execution point
* represented by this stack trace element is a native method.
*
* @return {@code true} if the method containing the execution point
* represented by this stack trace element is a native method.
*/
public boolean
isNativeMethod() {
return
lineNumber == -2;
}
/**
* Returns a string representation of this stack trace element. The
* format of this string depends on the implementation, but the following
* examples may be regarded as typical:
* <ul>
* <li>
* {@code "MyClass.mash(MyClass.java:9)"} - Here, {@code "MyClass"}
* is the <i>fully-qualified name</i> of the class containing the
* execution point represented by this stack trace element,
* {@code "mash"} is the name of the method containing the execution
* point, {@code "MyClass.java"} is the source file containing the
* execution point, and {@code "9"} is the line number of the source
* line containing the execution point.
* <li>
* {@code "MyClass.mash(MyClass.java)"} - As above, but the line
* number is unavailable.
* <li>
* {@code "MyClass.mash(Unknown Source)"} - As above, but neither
* the file name nor the line number are available.
* <li>
* {@code "MyClass.mash(Native Method)"} - As above, but neither
* the file name nor the line number are available, and the method
* containing the execution point is known to be a native method.
* </ul>
* @see Throwable#printStackTrace()
*/
public
String toString() {
return
getClassName() + "." +
methodName +
(
isNativeMethod() ? "(Native Method)" :
(
fileName != null &&
lineNumber >= 0 ?
"(" +
fileName + ":" +
lineNumber + ")" :
(
fileName != null ? "("+
fileName+")" : "(Unknown Source)")));
}
/**
* Returns true if the specified object is another
* {@code StackTraceElement} instance representing the same execution
* point as this instance. Two stack trace elements {@code a} and
* {@code b} are equal if and only if:
* <pre>{@code
* equals(a.getFileName(), b.getFileName()) &&
* a.getLineNumber() == b.getLineNumber()) &&
* equals(a.getClassName(), b.getClassName()) &&
* equals(a.getMethodName(), b.getMethodName())
* }</pre>
* where {@code equals} has the semantics of {@link
* java.util.Objects#equals(Object, Object) Objects.equals}.
*
* @param obj the object to be compared with this stack trace element.
* @return true if the specified object is another
* {@code StackTraceElement} instance representing the same
* execution point as this instance.
*/
public boolean
equals(
Object obj) {
if (
obj==this)
return true;
if (!(
obj instanceof
StackTraceElement))
return false;
StackTraceElement e = (
StackTraceElement)
obj;
return
e.
declaringClass.
equals(
declaringClass) &&
e.
lineNumber ==
lineNumber &&
Objects.
equals(
methodName,
e.
methodName) &&
Objects.
equals(
fileName,
e.
fileName);
}
/**
* Returns a hash code value for this stack trace element.
*/
public int
hashCode() {
int
result = 31*
declaringClass.
hashCode() +
methodName.
hashCode();
result = 31*
result +
Objects.
hashCode(
fileName);
result = 31*
result +
lineNumber;
return
result;
}
private static final long
serialVersionUID = 6992337162326171013L;
}