/*
* Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
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*
*
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*
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*
*
*
*
*/
package java.util;
import java.io.*;
import java.util.concurrent.atomic.
AtomicLong;
import java.util.function.
DoubleConsumer;
import java.util.function.
IntConsumer;
import java.util.function.
LongConsumer;
import java.util.stream.
DoubleStream;
import java.util.stream.
IntStream;
import java.util.stream.
LongStream;
import java.util.stream.
StreamSupport;
import sun.misc.
Unsafe;
/**
* An instance of this class is used to generate a stream of
* pseudorandom numbers. The class uses a 48-bit seed, which is
* modified using a linear congruential formula. (See Donald Knuth,
* <i>The Art of Computer Programming, Volume 2</i>, Section 3.2.1.)
* <p>
* If two instances of {@code Random} are created with the same
* seed, and the same sequence of method calls is made for each, they
* will generate and return identical sequences of numbers. In order to
* guarantee this property, particular algorithms are specified for the
* class {@code Random}. Java implementations must use all the algorithms
* shown here for the class {@code Random}, for the sake of absolute
* portability of Java code. However, subclasses of class {@code Random}
* are permitted to use other algorithms, so long as they adhere to the
* general contracts for all the methods.
* <p>
* The algorithms implemented by class {@code Random} use a
* {@code protected} utility method that on each invocation can supply
* up to 32 pseudorandomly generated bits.
* <p>
* Many applications will find the method {@link Math#random} simpler to use.
*
* <p>Instances of {@code java.util.Random} are threadsafe.
* However, the concurrent use of the same {@code java.util.Random}
* instance across threads may encounter contention and consequent
* poor performance. Consider instead using
* {@link java.util.concurrent.ThreadLocalRandom} in multithreaded
* designs.
*
* <p>Instances of {@code java.util.Random} are not cryptographically
* secure. Consider instead using {@link java.security.SecureRandom} to
* get a cryptographically secure pseudo-random number generator for use
* by security-sensitive applications.
*
* @author Frank Yellin
* @since 1.0
*/
public
class
Random implements java.io.
Serializable {
/** use serialVersionUID from JDK 1.1 for interoperability */
static final long
serialVersionUID = 3905348978240129619L;
/**
* The internal state associated with this pseudorandom number generator.
* (The specs for the methods in this class describe the ongoing
* computation of this value.)
*/
private final
AtomicLong seed;
private static final long
multiplier = 0x5DEECE66DL;
private static final long
addend = 0xBL;
private static final long
mask = (1L << 48) - 1;
private static final double
DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53)
// IllegalArgumentException messages
static final
String BadBound = "bound must be positive";
static final
String BadRange = "bound must be greater than origin";
static final
String BadSize = "size must be non-negative";
/**
* Creates a new random number generator. This constructor sets
* the seed of the random number generator to a value very likely
* to be distinct from any other invocation of this constructor.
*/
public
Random() {
this(
seedUniquifier() ^
System.
nanoTime());
}
private static long
seedUniquifier() {
// L'Ecuyer, "Tables of Linear Congruential Generators of
// Different Sizes and Good Lattice Structure", 1999
for (;;) {
long
current =
seedUniquifier.
get();
long
next =
current * 181783497276652981L;
if (
seedUniquifier.
compareAndSet(
current,
next))
return
next;
}
}
private static final
AtomicLong seedUniquifier
= new
AtomicLong(8682522807148012L);
/**
* Creates a new random number generator using a single {@code long} seed.
* The seed is the initial value of the internal state of the pseudorandom
* number generator which is maintained by method {@link #next}.
*
* <p>The invocation {@code new Random(seed)} is equivalent to:
* <pre> {@code
* Random rnd = new Random();
* rnd.setSeed(seed);}</pre>
*
* @param seed the initial seed
* @see #setSeed(long)
*/
public
Random(long
seed) {
if (
getClass() ==
Random.class)
this.
seed = new
AtomicLong(
initialScramble(
seed));
else {
// subclass might have overriden setSeed
this.
seed = new
AtomicLong();
setSeed(
seed);
}
}
private static long
initialScramble(long
seed) {
return (
seed ^
multiplier) &
mask;
}
/**
* Sets the seed of this random number generator using a single
* {@code long} seed. The general contract of {@code setSeed} is
* that it alters the state of this random number generator object
* so as to be in exactly the same state as if it had just been
* created with the argument {@code seed} as a seed. The method
* {@code setSeed} is implemented by class {@code Random} by
* atomically updating the seed to
* <pre>{@code (seed ^ 0x5DEECE66DL) & ((1L << 48) - 1)}</pre>
* and clearing the {@code haveNextNextGaussian} flag used by {@link
* #nextGaussian}.
*
* <p>The implementation of {@code setSeed} by class {@code Random}
* happens to use only 48 bits of the given seed. In general, however,
* an overriding method may use all 64 bits of the {@code long}
* argument as a seed value.
*
* @param seed the initial seed
*/
synchronized public void
setSeed(long
seed) {
this.
seed.
set(
initialScramble(
seed));
haveNextNextGaussian = false;
}
/**
* Generates the next pseudorandom number. Subclasses should
* override this, as this is used by all other methods.
*
* <p>The general contract of {@code next} is that it returns an
* {@code int} value and if the argument {@code bits} is between
* {@code 1} and {@code 32} (inclusive), then that many low-order
* bits of the returned value will be (approximately) independently
* chosen bit values, each of which is (approximately) equally
* likely to be {@code 0} or {@code 1}. The method {@code next} is
* implemented by class {@code Random} by atomically updating the seed to
* <pre>{@code (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)}</pre>
* and returning
* <pre>{@code (int)(seed >>> (48 - bits))}.</pre>
*
* This is a linear congruential pseudorandom number generator, as
* defined by D. H. Lehmer and described by Donald E. Knuth in
* <i>The Art of Computer Programming,</i> Volume 3:
* <i>Seminumerical Algorithms</i>, section 3.2.1.
*
* @param bits random bits
* @return the next pseudorandom value from this random number
* generator's sequence
* @since 1.1
*/
protected int
next(int
bits) {
long
oldseed,
nextseed;
AtomicLong seed = this.
seed;
do {
oldseed =
seed.
get();
nextseed = (
oldseed *
multiplier +
addend) &
mask;
} while (!
seed.
compareAndSet(
oldseed,
nextseed));
return (int)(
nextseed >>> (48 -
bits));
}
/**
* Generates random bytes and places them into a user-supplied
* byte array. The number of random bytes produced is equal to
* the length of the byte array.
*
* <p>The method {@code nextBytes} is implemented by class {@code Random}
* as if by:
* <pre> {@code
* public void nextBytes(byte[] bytes) {
* for (int i = 0; i < bytes.length; )
* for (int rnd = nextInt(), n = Math.min(bytes.length - i, 4);
* n-- > 0; rnd >>= 8)
* bytes[i++] = (byte)rnd;
* }}</pre>
*
* @param bytes the byte array to fill with random bytes
* @throws NullPointerException if the byte array is null
* @since 1.1
*/
public void
nextBytes(byte[]
bytes) {
for (int
i = 0,
len =
bytes.length;
i <
len; )
for (int
rnd =
nextInt(),
n =
Math.
min(
len -
i,
Integer.
SIZE/
Byte.
SIZE);
n-- > 0;
rnd >>=
Byte.
SIZE)
bytes[
i++] = (byte)
rnd;
}
/**
* The form of nextLong used by LongStream Spliterators. If
* origin is greater than bound, acts as unbounded form of
* nextLong, else as bounded form.
*
* @param origin the least value, unless greater than bound
* @param bound the upper bound (exclusive), must not equal origin
* @return a pseudorandom value
*/
final long
internalNextLong(long
origin, long
bound) {
long
r =
nextLong();
if (
origin <
bound) {
long
n =
bound -
origin,
m =
n - 1;
if ((
n &
m) == 0L) // power of two
r = (
r &
m) +
origin;
else if (
n > 0L) { // reject over-represented candidates
for (long
u =
r >>> 1; // ensure nonnegative
u +
m - (
r =
u %
n) < 0L; // rejection check
u =
nextLong() >>> 1) // retry
;
r +=
origin;
}
else { // range not representable as long
while (
r <
origin ||
r >=
bound)
r =
nextLong();
}
}
return
r;
}
/**
* The form of nextInt used by IntStream Spliterators.
* For the unbounded case: uses nextInt().
* For the bounded case with representable range: uses nextInt(int bound)
* For the bounded case with unrepresentable range: uses nextInt()
*
* @param origin the least value, unless greater than bound
* @param bound the upper bound (exclusive), must not equal origin
* @return a pseudorandom value
*/
final int
internalNextInt(int
origin, int
bound) {
if (
origin <
bound) {
int
n =
bound -
origin;
if (
n > 0) {
return
nextInt(
n) +
origin;
}
else { // range not representable as int
int
r;
do {
r =
nextInt();
} while (
r <
origin ||
r >=
bound);
return
r;
}
}
else {
return
nextInt();
}
}
/**
* The form of nextDouble used by DoubleStream Spliterators.
*
* @param origin the least value, unless greater than bound
* @param bound the upper bound (exclusive), must not equal origin
* @return a pseudorandom value
*/
final double
internalNextDouble(double
origin, double
bound) {
double
r =
nextDouble();
if (
origin <
bound) {
r =
r * (
bound -
origin) +
origin;
if (
r >=
bound) // correct for rounding
r =
Double.
longBitsToDouble(
Double.
doubleToLongBits(
bound) - 1);
}
return
r;
}
/**
* Returns the next pseudorandom, uniformly distributed {@code int}
* value from this random number generator's sequence. The general
* contract of {@code nextInt} is that one {@code int} value is
* pseudorandomly generated and returned. All 2<sup>32</sup> possible
* {@code int} values are produced with (approximately) equal probability.
*
* <p>The method {@code nextInt} is implemented by class {@code Random}
* as if by:
* <pre> {@code
* public int nextInt() {
* return next(32);
* }}</pre>
*
* @return the next pseudorandom, uniformly distributed {@code int}
* value from this random number generator's sequence
*/
public int
nextInt() {
return
next(32);
}
/**
* Returns a pseudorandom, uniformly distributed {@code int} value
* between 0 (inclusive) and the specified value (exclusive), drawn from
* this random number generator's sequence. The general contract of
* {@code nextInt} is that one {@code int} value in the specified range
* is pseudorandomly generated and returned. All {@code bound} possible
* {@code int} values are produced with (approximately) equal
* probability. The method {@code nextInt(int bound)} is implemented by
* class {@code Random} as if by:
* <pre> {@code
* public int nextInt(int bound) {
* if (bound <= 0)
* throw new IllegalArgumentException("bound must be positive");
*
* if ((bound & -bound) == bound) // i.e., bound is a power of 2
* return (int)((bound * (long)next(31)) >> 31);
*
* int bits, val;
* do {
* bits = next(31);
* val = bits % bound;
* } while (bits - val + (bound-1) < 0);
* return val;
* }}</pre>
*
* <p>The hedge "approximately" is used in the foregoing description only
* because the next method is only approximately an unbiased source of
* independently chosen bits. If it were a perfect source of randomly
* chosen bits, then the algorithm shown would choose {@code int}
* values from the stated range with perfect uniformity.
* <p>
* The algorithm is slightly tricky. It rejects values that would result
* in an uneven distribution (due to the fact that 2^31 is not divisible
* by n). The probability of a value being rejected depends on n. The
* worst case is n=2^30+1, for which the probability of a reject is 1/2,
* and the expected number of iterations before the loop terminates is 2.
* <p>
* The algorithm treats the case where n is a power of two specially: it
* returns the correct number of high-order bits from the underlying
* pseudo-random number generator. In the absence of special treatment,
* the correct number of <i>low-order</i> bits would be returned. Linear
* congruential pseudo-random number generators such as the one
* implemented by this class are known to have short periods in the
* sequence of values of their low-order bits. Thus, this special case
* greatly increases the length of the sequence of values returned by
* successive calls to this method if n is a small power of two.
*
* @param bound the upper bound (exclusive). Must be positive.
* @return the next pseudorandom, uniformly distributed {@code int}
* value between zero (inclusive) and {@code bound} (exclusive)
* from this random number generator's sequence
* @throws IllegalArgumentException if bound is not positive
* @since 1.2
*/
public int
nextInt(int
bound) {
if (
bound <= 0)
throw new
IllegalArgumentException(
BadBound);
int
r =
next(31);
int
m =
bound - 1;
if ((
bound &
m) == 0) // i.e., bound is a power of 2
r = (int)((
bound * (long)
r) >> 31);
else {
for (int
u =
r;
u - (
r =
u %
bound) +
m < 0;
u =
next(31))
;
}
return
r;
}
/**
* Returns the next pseudorandom, uniformly distributed {@code long}
* value from this random number generator's sequence. The general
* contract of {@code nextLong} is that one {@code long} value is
* pseudorandomly generated and returned.
*
* <p>The method {@code nextLong} is implemented by class {@code Random}
* as if by:
* <pre> {@code
* public long nextLong() {
* return ((long)next(32) << 32) + next(32);
* }}</pre>
*
* Because class {@code Random} uses a seed with only 48 bits,
* this algorithm will not return all possible {@code long} values.
*
* @return the next pseudorandom, uniformly distributed {@code long}
* value from this random number generator's sequence
*/
public long
nextLong() {
// it's okay that the bottom word remains signed.
return ((long)(
next(32)) << 32) +
next(32);
}
/**
* Returns the next pseudorandom, uniformly distributed
* {@code boolean} value from this random number generator's
* sequence. The general contract of {@code nextBoolean} is that one
* {@code boolean} value is pseudorandomly generated and returned. The
* values {@code true} and {@code false} are produced with
* (approximately) equal probability.
*
* <p>The method {@code nextBoolean} is implemented by class {@code Random}
* as if by:
* <pre> {@code
* public boolean nextBoolean() {
* return next(1) != 0;
* }}</pre>
*
* @return the next pseudorandom, uniformly distributed
* {@code boolean} value from this random number generator's
* sequence
* @since 1.2
*/
public boolean
nextBoolean() {
return
next(1) != 0;
}
/**
* Returns the next pseudorandom, uniformly distributed {@code float}
* value between {@code 0.0} and {@code 1.0} from this random
* number generator's sequence.
*
* <p>The general contract of {@code nextFloat} is that one
* {@code float} value, chosen (approximately) uniformly from the
* range {@code 0.0f} (inclusive) to {@code 1.0f} (exclusive), is
* pseudorandomly generated and returned. All 2<sup>24</sup> possible
* {@code float} values of the form <i>m x </i>2<sup>-24</sup>,
* where <i>m</i> is a positive integer less than 2<sup>24</sup>, are
* produced with (approximately) equal probability.
*
* <p>The method {@code nextFloat} is implemented by class {@code Random}
* as if by:
* <pre> {@code
* public float nextFloat() {
* return next(24) / ((float)(1 << 24));
* }}</pre>
*
* <p>The hedge "approximately" is used in the foregoing description only
* because the next method is only approximately an unbiased source of
* independently chosen bits. If it were a perfect source of randomly
* chosen bits, then the algorithm shown would choose {@code float}
* values from the stated range with perfect uniformity.<p>
* [In early versions of Java, the result was incorrectly calculated as:
* <pre> {@code
* return next(30) / ((float)(1 << 30));}</pre>
* This might seem to be equivalent, if not better, but in fact it
* introduced a slight nonuniformity because of the bias in the rounding
* of floating-point numbers: it was slightly more likely that the
* low-order bit of the significand would be 0 than that it would be 1.]
*
* @return the next pseudorandom, uniformly distributed {@code float}
* value between {@code 0.0} and {@code 1.0} from this
* random number generator's sequence
*/
public float
nextFloat() {
return
next(24) / ((float)(1 << 24));
}
/**
* Returns the next pseudorandom, uniformly distributed
* {@code double} value between {@code 0.0} and
* {@code 1.0} from this random number generator's sequence.
*
* <p>The general contract of {@code nextDouble} is that one
* {@code double} value, chosen (approximately) uniformly from the
* range {@code 0.0d} (inclusive) to {@code 1.0d} (exclusive), is
* pseudorandomly generated and returned.
*
* <p>The method {@code nextDouble} is implemented by class {@code Random}
* as if by:
* <pre> {@code
* public double nextDouble() {
* return (((long)next(26) << 27) + next(27))
* / (double)(1L << 53);
* }}</pre>
*
* <p>The hedge "approximately" is used in the foregoing description only
* because the {@code next} method is only approximately an unbiased
* source of independently chosen bits. If it were a perfect source of
* randomly chosen bits, then the algorithm shown would choose
* {@code double} values from the stated range with perfect uniformity.
* <p>[In early versions of Java, the result was incorrectly calculated as:
* <pre> {@code
* return (((long)next(27) << 27) + next(27))
* / (double)(1L << 54);}</pre>
* This might seem to be equivalent, if not better, but in fact it
* introduced a large nonuniformity because of the bias in the rounding
* of floating-point numbers: it was three times as likely that the
* low-order bit of the significand would be 0 than that it would be 1!
* This nonuniformity probably doesn't matter much in practice, but we
* strive for perfection.]
*
* @return the next pseudorandom, uniformly distributed {@code double}
* value between {@code 0.0} and {@code 1.0} from this
* random number generator's sequence
* @see Math#random
*/
public double
nextDouble() {
return (((long)(
next(26)) << 27) +
next(27)) *
DOUBLE_UNIT;
}
private double
nextNextGaussian;
private boolean
haveNextNextGaussian = false;
/**
* Returns the next pseudorandom, Gaussian ("normally") distributed
* {@code double} value with mean {@code 0.0} and standard
* deviation {@code 1.0} from this random number generator's sequence.
* <p>
* The general contract of {@code nextGaussian} is that one
* {@code double} value, chosen from (approximately) the usual
* normal distribution with mean {@code 0.0} and standard deviation
* {@code 1.0}, is pseudorandomly generated and returned.
*
* <p>The method {@code nextGaussian} is implemented by class
* {@code Random} as if by a threadsafe version of the following:
* <pre> {@code
* private double nextNextGaussian;
* private boolean haveNextNextGaussian = false;
*
* public double nextGaussian() {
* if (haveNextNextGaussian) {
* haveNextNextGaussian = false;
* return nextNextGaussian;
* } else {
* double v1, v2, s;
* do {
* v1 = 2 * nextDouble() - 1; // between -1.0 and 1.0
* v2 = 2 * nextDouble() - 1; // between -1.0 and 1.0
* s = v1 * v1 + v2 * v2;
* } while (s >= 1 || s == 0);
* double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
* nextNextGaussian = v2 * multiplier;
* haveNextNextGaussian = true;
* return v1 * multiplier;
* }
* }}</pre>
* This uses the <i>polar method</i> of G. E. P. Box, M. E. Muller, and
* G. Marsaglia, as described by Donald E. Knuth in <i>The Art of
* Computer Programming</i>, Volume 3: <i>Seminumerical Algorithms</i>,
* section 3.4.1, subsection C, algorithm P. Note that it generates two
* independent values at the cost of only one call to {@code StrictMath.log}
* and one call to {@code StrictMath.sqrt}.
*
* @return the next pseudorandom, Gaussian ("normally") distributed
* {@code double} value with mean {@code 0.0} and
* standard deviation {@code 1.0} from this random number
* generator's sequence
*/
synchronized public double
nextGaussian() {
// See Knuth, ACP, Section 3.4.1 Algorithm C.
if (
haveNextNextGaussian) {
haveNextNextGaussian = false;
return
nextNextGaussian;
} else {
double
v1,
v2,
s;
do {
v1 = 2 *
nextDouble() - 1; // between -1 and 1
v2 = 2 *
nextDouble() - 1; // between -1 and 1
s =
v1 *
v1 +
v2 *
v2;
} while (
s >= 1 ||
s == 0);
double
multiplier =
StrictMath.
sqrt(-2 *
StrictMath.
log(
s)/
s);
nextNextGaussian =
v2 *
multiplier;
haveNextNextGaussian = true;
return
v1 *
multiplier;
}
}
// stream methods, coded in a way intended to better isolate for
// maintenance purposes the small differences across forms.
/**
* Returns a stream producing the given {@code streamSize} number of
* pseudorandom {@code int} values.
*
* <p>A pseudorandom {@code int} value is generated as if it's the result of
* calling the method {@link #nextInt()}.
*
* @param streamSize the number of values to generate
* @return a stream of pseudorandom {@code int} values
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
* @since 1.8
*/
public
IntStream ints(long
streamSize) {
if (
streamSize < 0L)
throw new
IllegalArgumentException(
BadSize);
return
StreamSupport.
intStream
(new
RandomIntsSpliterator
(this, 0L,
streamSize,
Integer.
MAX_VALUE, 0),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code int}
* values.
*
* <p>A pseudorandom {@code int} value is generated as if it's the result of
* calling the method {@link #nextInt()}.
*
* @implNote This method is implemented to be equivalent to {@code
* ints(Long.MAX_VALUE)}.
*
* @return a stream of pseudorandom {@code int} values
* @since 1.8
*/
public
IntStream ints() {
return
StreamSupport.
intStream
(new
RandomIntsSpliterator
(this, 0L,
Long.
MAX_VALUE,
Integer.
MAX_VALUE, 0),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number
* of pseudorandom {@code int} values, each conforming to the given
* origin (inclusive) and bound (exclusive).
*
* <p>A pseudorandom {@code int} value is generated as if it's the result of
* calling the following method with the origin and bound:
* <pre> {@code
* int nextInt(int origin, int bound) {
* int n = bound - origin;
* if (n > 0) {
* return nextInt(n) + origin;
* }
* else { // range not representable as int
* int r;
* do {
* r = nextInt();
* } while (r < origin || r >= bound);
* return r;
* }
* }}</pre>
*
* @param streamSize the number of values to generate
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code int} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero, or {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
* @since 1.8
*/
public
IntStream ints(long
streamSize, int
randomNumberOrigin,
int
randomNumberBound) {
if (
streamSize < 0L)
throw new
IllegalArgumentException(
BadSize);
if (
randomNumberOrigin >=
randomNumberBound)
throw new
IllegalArgumentException(
BadRange);
return
StreamSupport.
intStream
(new
RandomIntsSpliterator
(this, 0L,
streamSize,
randomNumberOrigin,
randomNumberBound),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* int} values, each conforming to the given origin (inclusive) and bound
* (exclusive).
*
* <p>A pseudorandom {@code int} value is generated as if it's the result of
* calling the following method with the origin and bound:
* <pre> {@code
* int nextInt(int origin, int bound) {
* int n = bound - origin;
* if (n > 0) {
* return nextInt(n) + origin;
* }
* else { // range not representable as int
* int r;
* do {
* r = nextInt();
* } while (r < origin || r >= bound);
* return r;
* }
* }}</pre>
*
* @implNote This method is implemented to be equivalent to {@code
* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
*
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code int} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
* @since 1.8
*/
public
IntStream ints(int
randomNumberOrigin, int
randomNumberBound) {
if (
randomNumberOrigin >=
randomNumberBound)
throw new
IllegalArgumentException(
BadRange);
return
StreamSupport.
intStream
(new
RandomIntsSpliterator
(this, 0L,
Long.
MAX_VALUE,
randomNumberOrigin,
randomNumberBound),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* pseudorandom {@code long} values.
*
* <p>A pseudorandom {@code long} value is generated as if it's the result
* of calling the method {@link #nextLong()}.
*
* @param streamSize the number of values to generate
* @return a stream of pseudorandom {@code long} values
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
* @since 1.8
*/
public
LongStream longs(long
streamSize) {
if (
streamSize < 0L)
throw new
IllegalArgumentException(
BadSize);
return
StreamSupport.
longStream
(new
RandomLongsSpliterator
(this, 0L,
streamSize,
Long.
MAX_VALUE, 0L),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code long}
* values.
*
* <p>A pseudorandom {@code long} value is generated as if it's the result
* of calling the method {@link #nextLong()}.
*
* @implNote This method is implemented to be equivalent to {@code
* longs(Long.MAX_VALUE)}.
*
* @return a stream of pseudorandom {@code long} values
* @since 1.8
*/
public
LongStream longs() {
return
StreamSupport.
longStream
(new
RandomLongsSpliterator
(this, 0L,
Long.
MAX_VALUE,
Long.
MAX_VALUE, 0L),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* pseudorandom {@code long}, each conforming to the given origin
* (inclusive) and bound (exclusive).
*
* <p>A pseudorandom {@code long} value is generated as if it's the result
* of calling the following method with the origin and bound:
* <pre> {@code
* long nextLong(long origin, long bound) {
* long r = nextLong();
* long n = bound - origin, m = n - 1;
* if ((n & m) == 0L) // power of two
* r = (r & m) + origin;
* else if (n > 0L) { // reject over-represented candidates
* for (long u = r >>> 1; // ensure nonnegative
* u + m - (r = u % n) < 0L; // rejection check
* u = nextLong() >>> 1) // retry
* ;
* r += origin;
* }
* else { // range not representable as long
* while (r < origin || r >= bound)
* r = nextLong();
* }
* return r;
* }}</pre>
*
* @param streamSize the number of values to generate
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code long} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero, or {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
* @since 1.8
*/
public
LongStream longs(long
streamSize, long
randomNumberOrigin,
long
randomNumberBound) {
if (
streamSize < 0L)
throw new
IllegalArgumentException(
BadSize);
if (
randomNumberOrigin >=
randomNumberBound)
throw new
IllegalArgumentException(
BadRange);
return
StreamSupport.
longStream
(new
RandomLongsSpliterator
(this, 0L,
streamSize,
randomNumberOrigin,
randomNumberBound),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* long} values, each conforming to the given origin (inclusive) and bound
* (exclusive).
*
* <p>A pseudorandom {@code long} value is generated as if it's the result
* of calling the following method with the origin and bound:
* <pre> {@code
* long nextLong(long origin, long bound) {
* long r = nextLong();
* long n = bound - origin, m = n - 1;
* if ((n & m) == 0L) // power of two
* r = (r & m) + origin;
* else if (n > 0L) { // reject over-represented candidates
* for (long u = r >>> 1; // ensure nonnegative
* u + m - (r = u % n) < 0L; // rejection check
* u = nextLong() >>> 1) // retry
* ;
* r += origin;
* }
* else { // range not representable as long
* while (r < origin || r >= bound)
* r = nextLong();
* }
* return r;
* }}</pre>
*
* @implNote This method is implemented to be equivalent to {@code
* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
*
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code long} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
* @since 1.8
*/
public
LongStream longs(long
randomNumberOrigin, long
randomNumberBound) {
if (
randomNumberOrigin >=
randomNumberBound)
throw new
IllegalArgumentException(
BadRange);
return
StreamSupport.
longStream
(new
RandomLongsSpliterator
(this, 0L,
Long.
MAX_VALUE,
randomNumberOrigin,
randomNumberBound),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* pseudorandom {@code double} values, each between zero
* (inclusive) and one (exclusive).
*
* <p>A pseudorandom {@code double} value is generated as if it's the result
* of calling the method {@link #nextDouble()}.
*
* @param streamSize the number of values to generate
* @return a stream of {@code double} values
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
* @since 1.8
*/
public
DoubleStream doubles(long
streamSize) {
if (
streamSize < 0L)
throw new
IllegalArgumentException(
BadSize);
return
StreamSupport.
doubleStream
(new
RandomDoublesSpliterator
(this, 0L,
streamSize,
Double.
MAX_VALUE, 0.0),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* double} values, each between zero (inclusive) and one
* (exclusive).
*
* <p>A pseudorandom {@code double} value is generated as if it's the result
* of calling the method {@link #nextDouble()}.
*
* @implNote This method is implemented to be equivalent to {@code
* doubles(Long.MAX_VALUE)}.
*
* @return a stream of pseudorandom {@code double} values
* @since 1.8
*/
public
DoubleStream doubles() {
return
StreamSupport.
doubleStream
(new
RandomDoublesSpliterator
(this, 0L,
Long.
MAX_VALUE,
Double.
MAX_VALUE, 0.0),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* pseudorandom {@code double} values, each conforming to the given origin
* (inclusive) and bound (exclusive).
*
* <p>A pseudorandom {@code double} value is generated as if it's the result
* of calling the following method with the origin and bound:
* <pre> {@code
* double nextDouble(double origin, double bound) {
* double r = nextDouble();
* r = r * (bound - origin) + origin;
* if (r >= bound) // correct for rounding
* r = Math.nextDown(bound);
* return r;
* }}</pre>
*
* @param streamSize the number of values to generate
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code double} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
* @throws IllegalArgumentException if {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
* @since 1.8
*/
public
DoubleStream doubles(long
streamSize, double
randomNumberOrigin,
double
randomNumberBound) {
if (
streamSize < 0L)
throw new
IllegalArgumentException(
BadSize);
if (!(
randomNumberOrigin <
randomNumberBound))
throw new
IllegalArgumentException(
BadRange);
return
StreamSupport.
doubleStream
(new
RandomDoublesSpliterator
(this, 0L,
streamSize,
randomNumberOrigin,
randomNumberBound),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* double} values, each conforming to the given origin (inclusive) and bound
* (exclusive).
*
* <p>A pseudorandom {@code double} value is generated as if it's the result
* of calling the following method with the origin and bound:
* <pre> {@code
* double nextDouble(double origin, double bound) {
* double r = nextDouble();
* r = r * (bound - origin) + origin;
* if (r >= bound) // correct for rounding
* r = Math.nextDown(bound);
* return r;
* }}</pre>
*
* @implNote This method is implemented to be equivalent to {@code
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
*
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code double} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
* @since 1.8
*/
public
DoubleStream doubles(double
randomNumberOrigin, double
randomNumberBound) {
if (!(
randomNumberOrigin <
randomNumberBound))
throw new
IllegalArgumentException(
BadRange);
return
StreamSupport.
doubleStream
(new
RandomDoublesSpliterator
(this, 0L,
Long.
MAX_VALUE,
randomNumberOrigin,
randomNumberBound),
false);
}
/**
* Spliterator for int streams. We multiplex the four int
* versions into one class by treating a bound less than origin as
* unbounded, and also by treating "infinite" as equivalent to
* Long.MAX_VALUE. For splits, it uses the standard divide-by-two
* approach. The long and double versions of this class are
* identical except for types.
*/
static final class
RandomIntsSpliterator implements
Spliterator.
OfInt {
final
Random rng;
long
index;
final long
fence;
final int
origin;
final int
bound;
RandomIntsSpliterator(
Random rng, long
index, long
fence,
int
origin, int
bound) {
this.
rng =
rng; this.
index =
index; this.
fence =
fence;
this.
origin =
origin; this.
bound =
bound;
}
public
RandomIntsSpliterator trySplit() {
long
i =
index,
m = (
i +
fence) >>> 1;
return (
m <=
i) ? null :
new
RandomIntsSpliterator(
rng,
i,
index =
m,
origin,
bound);
}
public long
estimateSize() {
return
fence -
index;
}
public int
characteristics() {
return (
Spliterator.
SIZED |
Spliterator.
SUBSIZED |
Spliterator.
NONNULL |
Spliterator.
IMMUTABLE);
}
public boolean
tryAdvance(
IntConsumer consumer) {
if (
consumer == null) throw new
NullPointerException();
long
i =
index,
f =
fence;
if (
i <
f) {
consumer.
accept(
rng.
internalNextInt(
origin,
bound));
index =
i + 1;
return true;
}
return false;
}
public void
forEachRemaining(
IntConsumer consumer) {
if (
consumer == null) throw new
NullPointerException();
long
i =
index,
f =
fence;
if (
i <
f) {
index =
f;
Random r =
rng;
int
o =
origin,
b =
bound;
do {
consumer.
accept(
r.
internalNextInt(
o,
b));
} while (++
i <
f);
}
}
}
/**
* Spliterator for long streams.
*/
static final class
RandomLongsSpliterator implements
Spliterator.
OfLong {
final
Random rng;
long
index;
final long
fence;
final long
origin;
final long
bound;
RandomLongsSpliterator(
Random rng, long
index, long
fence,
long
origin, long
bound) {
this.
rng =
rng; this.
index =
index; this.
fence =
fence;
this.
origin =
origin; this.
bound =
bound;
}
public
RandomLongsSpliterator trySplit() {
long
i =
index,
m = (
i +
fence) >>> 1;
return (
m <=
i) ? null :
new
RandomLongsSpliterator(
rng,
i,
index =
m,
origin,
bound);
}
public long
estimateSize() {
return
fence -
index;
}
public int
characteristics() {
return (
Spliterator.
SIZED |
Spliterator.
SUBSIZED |
Spliterator.
NONNULL |
Spliterator.
IMMUTABLE);
}
public boolean
tryAdvance(
LongConsumer consumer) {
if (
consumer == null) throw new
NullPointerException();
long
i =
index,
f =
fence;
if (
i <
f) {
consumer.
accept(
rng.
internalNextLong(
origin,
bound));
index =
i + 1;
return true;
}
return false;
}
public void
forEachRemaining(
LongConsumer consumer) {
if (
consumer == null) throw new
NullPointerException();
long
i =
index,
f =
fence;
if (
i <
f) {
index =
f;
Random r =
rng;
long
o =
origin,
b =
bound;
do {
consumer.
accept(
r.
internalNextLong(
o,
b));
} while (++
i <
f);
}
}
}
/**
* Spliterator for double streams.
*/
static final class
RandomDoublesSpliterator implements
Spliterator.
OfDouble {
final
Random rng;
long
index;
final long
fence;
final double
origin;
final double
bound;
RandomDoublesSpliterator(
Random rng, long
index, long
fence,
double
origin, double
bound) {
this.
rng =
rng; this.
index =
index; this.
fence =
fence;
this.
origin =
origin; this.
bound =
bound;
}
public
RandomDoublesSpliterator trySplit() {
long
i =
index,
m = (
i +
fence) >>> 1;
return (
m <=
i) ? null :
new
RandomDoublesSpliterator(
rng,
i,
index =
m,
origin,
bound);
}
public long
estimateSize() {
return
fence -
index;
}
public int
characteristics() {
return (
Spliterator.
SIZED |
Spliterator.
SUBSIZED |
Spliterator.
NONNULL |
Spliterator.
IMMUTABLE);
}
public boolean
tryAdvance(
DoubleConsumer consumer) {
if (
consumer == null) throw new
NullPointerException();
long
i =
index,
f =
fence;
if (
i <
f) {
consumer.
accept(
rng.
internalNextDouble(
origin,
bound));
index =
i + 1;
return true;
}
return false;
}
public void
forEachRemaining(
DoubleConsumer consumer) {
if (
consumer == null) throw new
NullPointerException();
long
i =
index,
f =
fence;
if (
i <
f) {
index =
f;
Random r =
rng;
double
o =
origin,
b =
bound;
do {
consumer.
accept(
r.
internalNextDouble(
o,
b));
} while (++
i <
f);
}
}
}
/**
* Serializable fields for Random.
*
* @serialField seed long
* seed for random computations
* @serialField nextNextGaussian double
* next Gaussian to be returned
* @serialField haveNextNextGaussian boolean
* nextNextGaussian is valid
*/
private static final
ObjectStreamField[]
serialPersistentFields = {
new
ObjectStreamField("seed",
Long.
TYPE),
new
ObjectStreamField("nextNextGaussian",
Double.
TYPE),
new
ObjectStreamField("haveNextNextGaussian",
Boolean.
TYPE)
};
/**
* Reconstitute the {@code Random} instance from a stream (that is,
* deserialize it).
*/
private void
readObject(java.io.
ObjectInputStream s)
throws java.io.
IOException,
ClassNotFoundException {
ObjectInputStream.
GetField fields =
s.
readFields();
// The seed is read in as {@code long} for
// historical reasons, but it is converted to an AtomicLong.
long
seedVal =
fields.
get("seed", -1L);
if (
seedVal < 0)
throw new java.io.
StreamCorruptedException(
"Random: invalid seed");
resetSeed(
seedVal);
nextNextGaussian =
fields.
get("nextNextGaussian", 0.0);
haveNextNextGaussian =
fields.
get("haveNextNextGaussian", false);
}
/**
* Save the {@code Random} instance to a stream.
*/
synchronized private void
writeObject(
ObjectOutputStream s)
throws
IOException {
// set the values of the Serializable fields
ObjectOutputStream.
PutField fields =
s.
putFields();
// The seed is serialized as a long for historical reasons.
fields.
put("seed",
seed.
get());
fields.
put("nextNextGaussian",
nextNextGaussian);
fields.
put("haveNextNextGaussian",
haveNextNextGaussian);
// save them
s.
writeFields();
}
// Support for resetting seed while deserializing
private static final
Unsafe unsafe =
Unsafe.
getUnsafe();
private static final long
seedOffset;
static {
try {
seedOffset =
unsafe.
objectFieldOffset
(
Random.class.
getDeclaredField("seed"));
} catch (
Exception ex) { throw new
Error(
ex); }
}
private void
resetSeed(long
seedVal) {
unsafe.
putObjectVolatile(this,
seedOffset, new
AtomicLong(
seedVal));
}
}