Added in API level 1

Summary: Ctors | Methods | Protected Methods | Inherited Methods

Random

public class Random
extends Object implements RandomGenerator, Serializable

java.lang.Object
↳	java.util.Random

Known direct subclasses

SecureRandom, ThreadLocalRandom

SecureRandom	This class provides a cryptographically strong random number generator (RNG).
ThreadLocalRandom	A random number generator (with period 2⁶⁴) isolated to the current thread.

An instance of this class is used to generate a stream of pseudorandom numbers; its period is only 2⁴⁸. The class uses a 48-bit seed, which is modified using a linear congruential formula. (See Donald E. Knuth, The Art of Computer Programming, Volume 2, Third edition: Seminumerical Algorithms, Section 3.2.1.)

If two instances of 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 Random. Java implementations must use all the algorithms shown here for the class Random, for the sake of absolute portability of Java code. However, subclasses of class Random are permitted to use other algorithms, so long as they adhere to the general contracts for all the methods.

The algorithms implemented by class Random use a protected utility method that on each invocation can supply up to 32 pseudorandomly generated bits.

Many applications will find the method Math.random simpler to use.

Instances of java.util.Random are threadsafe. However, the concurrent use of the same java.util.Random instance across threads may encounter contention and consequent poor performance. Consider instead using ThreadLocalRandom in multithreaded designs.

Instances of java.util.Random are not cryptographically secure. Consider instead using SecureRandom to get a cryptographically secure pseudo-random number generator for use by security-sensitive applications.

Summary

Public constructors
`Random()` Creates a new random number generator.
`Random(long seed)` Creates a new random number generator using a single `long` seed.

Public methods
`DoubleStream`	`doubles(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandom `double` values, each between zero (inclusive) and one (exclusive).
`DoubleStream`	`doubles()` Returns an effectively unlimited stream of pseudorandom `double` values, each between zero (inclusive) and one (exclusive).
`DoubleStream`	`doubles(double randomNumberOrigin, double randomNumberBound)` Returns an effectively unlimited stream of pseudorandom `double` values, each conforming to the given origin (inclusive) and bound (exclusive).
`DoubleStream`	`doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandom `double` values, each conforming to the given origin (inclusive) and bound (exclusive).
`static Random`	`from(RandomGenerator generator)` Returns an instance of `Random` that delegates method calls to the `RandomGenerator` argument.
`IntStream`	`ints(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandom `int` values.
`IntStream`	`ints(int randomNumberOrigin, int randomNumberBound)` Returns an effectively unlimited stream of pseudorandom `int` values, each conforming to the given origin (inclusive) and bound (exclusive).
`IntStream`	`ints(long streamSize, int randomNumberOrigin, int randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandom `int` values, each conforming to the given origin (inclusive) and bound (exclusive).
`IntStream`	`ints()` Returns an effectively unlimited stream of pseudorandom `int` values.
`LongStream`	`longs()` Returns an effectively unlimited stream of pseudorandom `long` values.
`LongStream`	`longs(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandom `long` values.
`LongStream`	`longs(long randomNumberOrigin, long randomNumberBound)` Returns an effectively unlimited stream of pseudorandom `long` values, each conforming to the given origin (inclusive) and bound (exclusive).
`LongStream`	`longs(long streamSize, long randomNumberOrigin, long randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandom `long`, each conforming to the given origin (inclusive) and bound (exclusive).
`boolean`	`nextBoolean()` Returns the next pseudorandom, uniformly distributed `boolean` value from this random number generator's sequence.
`void`	`nextBytes(byte[] bytes)` Generates random bytes and places them into a user-supplied byte array.
`double`	`nextDouble()` Returns the next pseudorandom, uniformly distributed `double` value between `0.0` and `1.0` from this random number generator's sequence.
`float`	`nextFloat()` Returns the next pseudorandom, uniformly distributed `float` value between `0.0` and `1.0` from this random number generator's sequence.
`double`	`nextGaussian()` Returns the next pseudorandom, Gaussian ("normally") distributed `double` value with mean `0.0` and standard deviation `1.0` from this random number generator's sequence.
`int`	`nextInt()` Returns the next pseudorandom, uniformly distributed `int` value from this random number generator's sequence.
`int`	`nextInt(int bound)` Returns a pseudorandom, uniformly distributed `int` value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.
`long`	`nextLong()` Returns the next pseudorandom, uniformly distributed `long` value from this random number generator's sequence.
`void`	`setSeed(long seed)` Sets or updates the seed of this random number generator using the provided `long` seed value (optional operation).

Protected methods
`int`	`next(int bits)` Generates the next pseudorandom number.

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

From interface


        
          java.util.random.RandomGenerator

`default DoubleStream`	`doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `double` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default DoubleStream`	`doubles(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `double` values.
`default DoubleStream`	`doubles()` Returns an effectively unlimited stream of pseudorandomly chosen `double` values.
`default DoubleStream`	`doubles(double randomNumberOrigin, double randomNumberBound)` Returns an effectively unlimited stream of pseudorandomly chosen `double` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`static RandomGenerator`	`getDefault()` Returns a `RandomGenerator` meeting the minimal requirement of having an algorithm whose state bits are greater than or equal 64.
`default IntStream`	`ints(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `int` values.
`default IntStream`	`ints(int randomNumberOrigin, int randomNumberBound)` Returns an effectively unlimited stream of pseudorandomly chosen `int` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default IntStream`	`ints()` Returns an effectively unlimited stream of pseudorandomly chosen `int` values.
`default IntStream`	`ints(long streamSize, int randomNumberOrigin, int randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `int` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default boolean`	`isDeprecated()` Return true if the implementation of RandomGenerator (algorithm) has been marked for deprecation.
`default LongStream`	`longs(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `long` values.
`default LongStream`	`longs()` Returns an effectively unlimited stream of pseudorandomly chosen `long` values.
`default LongStream`	`longs(long randomNumberOrigin, long randomNumberBound)` Returns an effectively unlimited stream of pseudorandomly chosen `long` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default LongStream`	`longs(long streamSize, long randomNumberOrigin, long randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `long` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default boolean`	`nextBoolean()` Returns a pseudorandomly chosen `boolean` value.
`default void`	`nextBytes(byte[] bytes)` Fills a user-supplied byte array with generated byte values pseudorandomly chosen uniformly from the range of values between -128 (inclusive) and 127 (inclusive).
`default double`	`nextDouble()` Returns a pseudorandom `double` value between zero (inclusive) and one (exclusive).
`default double`	`nextDouble(double bound)` Returns a pseudorandomly chosen `double` value between zero (inclusive) and the specified bound (exclusive).
`default double`	`nextDouble(double origin, double bound)` Returns a pseudorandomly chosen `double` value between the specified origin (inclusive) and the specified bound (exclusive).
`default double`	`nextExponential()` Returns a nonnegative `double` value pseudorandomly chosen from an exponential distribution whose mean is 1.
`default float`	`nextFloat(float origin, float bound)` Returns a pseudorandomly chosen `float` value between the specified origin (inclusive) and the specified bound (exclusive).
`default float`	`nextFloat()` Returns a pseudorandom `float` value between zero (inclusive) and one (exclusive).
`default float`	`nextFloat(float bound)` Returns a pseudorandomly chosen `float` value between zero (inclusive) and the specified bound (exclusive).
`default double`	`nextGaussian(double mean, double stddev)` Returns a `double` value pseudorandomly chosen from a Gaussian (normal) distribution with a mean and standard deviation specified by the arguments.
`default double`	`nextGaussian()` Returns a `double` value pseudorandomly chosen from a Gaussian (normal) distribution whose mean is 0 and whose standard deviation is 1.
`default int`	`nextInt(int origin, int bound)` Returns a pseudorandomly chosen `int` value between the specified origin (inclusive) and the specified bound (exclusive).
`default int`	`nextInt()` Returns a pseudorandomly chosen `int` value.
`default int`	`nextInt(int bound)` Returns a pseudorandomly chosen `int` value between zero (inclusive) and the specified bound (exclusive).
`default long`	`nextLong(long origin, long bound)` Returns a pseudorandomly chosen `long` value between the specified origin (inclusive) and the specified bound (exclusive).
`default long`	`nextLong(long bound)` Returns a pseudorandomly chosen `long` value between zero (inclusive) and the specified bound (exclusive).
`abstract long`	`nextLong()` Returns a pseudorandomly chosen `long` value.
`static RandomGenerator`	`of(String name)` Returns an instance of `RandomGenerator` that utilizes the `name` algorithm.

Public constructors

Random

Added in API level 1

public Random ()

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.

Random

Added in API level 1

public Random (long seed)

Creates a new random number generator using a single long seed. The seed is the initial value of the internal state of the pseudorandom number generator which is maintained by method next(int).

Implementation Requirements:

The invocation new Random(seed) is equivalent to:

Random rnd = new Random();
 rnd.setSeed(seed);

Parameters
`seed`	`long`: the initial seed

See also:

setSeed(long)

Public methods

doubles

Added in API level 24

public DoubleStream doubles (long streamSize)

Returns a stream producing the given streamSize number of pseudorandom double values, each between zero (inclusive) and one (exclusive).

A pseudorandom double value is generated as if it's the result of calling the method nextDouble().

Parameters
`streamSize`	`long`: the number of values to generate

Returns
`DoubleStream`	a stream of `double` values

Throws
`IllegalArgumentException`	if `streamSize` is less than zero

doubles

Added in API level 24

public DoubleStream doubles ()

Returns an effectively unlimited stream of pseudorandom double values, each between zero (inclusive) and one (exclusive).

A pseudorandom double value is generated as if it's the result of calling the method nextDouble().

Implementation Note:

This method is implemented to be equivalent to doubles(Long.MAX_VALUE).

Returns
`DoubleStream`	a stream of pseudorandom `double` values

doubles

Added in API level 24

public DoubleStream doubles (double randomNumberOrigin, 
                double randomNumberBound)

Returns an effectively unlimited stream of pseudorandom double values, each conforming to the given origin (inclusive) and bound (exclusive).

Implementation Note:

This method is implemented to be equivalent to doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).

Parameters
`randomNumberOrigin`	`double`: the origin (inclusive) of each random value
`randomNumberBound`	`double`: the bound (exclusive) of each random value

Returns
`DoubleStream`	a stream of pseudorandom `double` values, each with the given origin (inclusive) and bound (exclusive)

Throws
`IllegalArgumentException`

doubles

Added in API level 24

public DoubleStream doubles (long streamSize, 
                double randomNumberOrigin, 
                double randomNumberBound)

Returns a stream producing the given streamSize number of pseudorandom double values, each conforming to the given origin (inclusive) and bound (exclusive).

Parameters
`streamSize`	`long`: the number of values to generate
`randomNumberOrigin`	`double`: the origin (inclusive) of each random value
`randomNumberBound`	`double`: the bound (exclusive) of each random value

Returns
`DoubleStream`	a stream of pseudorandom `double` values, each with the given origin (inclusive) and bound (exclusive)

Throws
`IllegalArgumentException`

from

Added in API level 36

public static Random from (RandomGenerator generator)

Returns an instance of Random that delegates method calls to the RandomGenerator argument. If the generator is an instance of Random, it is returned. Otherwise, this method returns an instance of Random that delegates all methods except setSeed to the generator. The returned instance's setSeed method always throws UnsupportedOperationException. The returned instance is not serializable.

Parameters
`generator`	`RandomGenerator`: the `RandomGenerator` calls are delegated to

Returns
`Random`	the delegating `Random` instance

Throws
`NullPointerException`	if generator is null

ints

Added in API level 24

public IntStream ints (long streamSize)

Returns a stream producing the given streamSize number of pseudorandom int values.

A pseudorandom int value is generated as if it's the result of calling the method nextInt().

Parameters
`streamSize`	`long`: the number of values to generate

Returns
`IntStream`	a stream of pseudorandom `int` values

Throws
`IllegalArgumentException`	if `streamSize` is less than zero

ints

Added in API level 24

public IntStream ints (int randomNumberOrigin, 
                int randomNumberBound)

Returns an effectively unlimited stream of pseudorandom int values, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom int value is generated as if it's the result of calling the following method with the origin and bound:

 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;
   }
 }

Implementation Note:

This method is implemented to be equivalent to ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).

Parameters
`randomNumberOrigin`	`int`: the origin (inclusive) of each random value
`randomNumberBound`	`int`: the bound (exclusive) of each random value

Returns
`IntStream`	a stream of pseudorandom `int` values, each with the given origin (inclusive) and bound (exclusive)

Throws
`IllegalArgumentException`	if `randomNumberOrigin` is greater than or equal to `randomNumberBound`

ints

Added in API level 24

public IntStream ints (long streamSize, 
                int randomNumberOrigin, 
                int randomNumberBound)

Returns a stream producing the given streamSize number of pseudorandom int values, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom int value is generated as if it's the result of calling the following method with the origin and bound:

 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;
   }
 }

Parameters
`streamSize`	`long`: the number of values to generate
`randomNumberOrigin`	`int`: the origin (inclusive) of each random value
`randomNumberBound`	`int`: the bound (exclusive) of each random value

Returns
`IntStream`	a stream of pseudorandom `int` values, each with the given origin (inclusive) and bound (exclusive)

Throws
`IllegalArgumentException`	if `streamSize` is less than zero, or `randomNumberOrigin` is greater than or equal to `randomNumberBound`

ints

Added in API level 24

public IntStream ints ()

Returns an effectively unlimited stream of pseudorandom int values.

A pseudorandom int value is generated as if it's the result of calling the method nextInt().

Implementation Note:

This method is implemented to be equivalent to ints(Long.MAX_VALUE).

Returns
`IntStream`	a stream of pseudorandom `int` values

longs

Added in API level 24

public LongStream longs ()

Returns an effectively unlimited stream of pseudorandom long values.

A pseudorandom long value is generated as if it's the result of calling the method nextLong().

Implementation Note:

This method is implemented to be equivalent to longs(Long.MAX_VALUE).

Returns
`LongStream`	a stream of pseudorandom `long` values

longs

Added in API level 24

public LongStream longs (long streamSize)

Returns a stream producing the given streamSize number of pseudorandom long values.

A pseudorandom long value is generated as if it's the result of calling the method nextLong().

Parameters
`streamSize`	`long`: the number of values to generate

Returns
`LongStream`	a stream of pseudorandom `long` values

Throws
`IllegalArgumentException`	if `streamSize` is less than zero

longs

Added in API level 24

public LongStream longs (long randomNumberOrigin, 
                long randomNumberBound)

Returns an effectively unlimited stream of pseudorandom long values, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom long value is generated as if it's the result of calling the following method with the origin and bound:

 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;
 }

Implementation Note:

This method is implemented to be equivalent to longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).

Parameters
`randomNumberOrigin`	`long`: the origin (inclusive) of each random value
`randomNumberBound`	`long`: the bound (exclusive) of each random value

Returns
`LongStream`	a stream of pseudorandom `long` values, each with the given origin (inclusive) and bound (exclusive)

Throws
`IllegalArgumentException`	if `randomNumberOrigin` is greater than or equal to `randomNumberBound`

longs

Added in API level 24

public LongStream longs (long streamSize, 
                long randomNumberOrigin, 
                long randomNumberBound)

Returns a stream producing the given streamSize number of pseudorandom long, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom long value is generated as if it's the result of calling the following method with the origin and bound:

 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;
 }

Parameters
`streamSize`	`long`: the number of values to generate
`randomNumberOrigin`	`long`: the origin (inclusive) of each random value
`randomNumberBound`	`long`: the bound (exclusive) of each random value

Returns
`LongStream`	a stream of pseudorandom `long` values, each with the given origin (inclusive) and bound (exclusive)

Throws
`IllegalArgumentException`	if `streamSize` is less than zero, or `randomNumberOrigin` is greater than or equal to `randomNumberBound`

nextBoolean

Added in API level 1

public boolean nextBoolean ()

Returns the next pseudorandom, uniformly distributed boolean value from this random number generator's sequence. The general contract of nextBoolean is that one boolean value is pseudorandomly generated and returned. The values true and false are produced with (approximately) equal probability.

Implementation Requirements:

The method nextBoolean is implemented by class Random as if by:
```
public boolean nextBoolean() {
   return next(1) != 0;
 }
```

Returns
`boolean`	the next pseudorandom, uniformly distributed `boolean` value from this random number generator's sequence

nextBytes

Added in API level 1

public void nextBytes (byte[] bytes)

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.

Implementation Requirements:

The method nextBytes is implemented by class Random as if by:

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;
 }

Parameters
`bytes`	`byte`: the byte array to fill with random bytes

Throws
`NullPointerException`	if the byte array is null

nextDouble

Added in API level 1

public double nextDouble ()

Returns the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence.

The general contract of nextDouble is that one double value, chosen (approximately) uniformly from the range 0.0d (inclusive) to 1.0d (exclusive), is pseudorandomly generated and returned.

Implementation Requirements:

The method nextDouble is implemented by class Random as if by:
```
public double nextDouble() {
   return (((long)next(26) << 27) + next(27))
     / (double)(1L << 53);
 }
```
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 double values from the stated range with perfect uniformity.
[In early versions of Java, the result was incorrectly calculated as:
```
 return (((long)next(27) << 27) + next(27)) / (double)(1L << 54);
```
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.]

Returns
`double`	the next pseudorandom, uniformly distributed `double` value between `0.0` and `1.0` from this random number generator's sequence

See also:

Math.random()

nextFloat

Added in API level 1

public float nextFloat ()

Returns the next pseudorandom, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence.

The general contract of nextFloat is that one float value, chosen (approximately) uniformly from the range 0.0f (inclusive) to 1.0f (exclusive), is pseudorandomly generated and returned. All 2²⁴ possible float values of the form m x 2^-24, where m is a positive integer less than 2²⁴, are produced with (approximately) equal probability.

Implementation Requirements:

The method nextFloat is implemented by class Random as if by:
```
public float nextFloat() {
   return next(24) / ((float)(1 << 24));
 }
```
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 float values from the stated range with perfect uniformity.
[In early versions of Java, the result was incorrectly calculated as:
```
 return next(30) / ((float)(1 << 30));
```
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.]

Returns
`float`	the next pseudorandom, uniformly distributed `float` value between `0.0f` and `1.0f` from this random number generator's sequence

nextGaussian

Added in API level 1

public double nextGaussian ()

Returns the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence.

The general contract of nextGaussian is that one double value, chosen from (approximately) the usual normal distribution with mean 0.0 and standard deviation 1.0, is pseudorandomly generated and returned.

Implementation Requirements:

The method nextGaussian is implemented by class Random as if by a threadsafe version of the following:

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;
   }
 }

This uses the polar method of G. E. P. Box, M. E. Muller, and G. Marsaglia, as described by Donald E. Knuth in The Art of Computer Programming, Volume 2, third edition: Seminumerical Algorithms, section 3.4.1, subsection C, algorithm P. Note that it generates two independent values at the cost of only one call to StrictMath.log and one call to StrictMath.sqrt.

Returns
`double`	the next pseudorandom, Gaussian ("normally") distributed `double` value with mean `0.0` and standard deviation `1.0` from this random number generator's sequence

nextInt

Added in API level 1

public int nextInt ()

Returns the next pseudorandom, uniformly distributed int value from this random number generator's sequence. The general contract of nextInt is that one int value is pseudorandomly generated and returned. All 2³² possible int values are produced with (approximately) equal probability.

Implementation Requirements:

The method nextInt is implemented by class Random as if by:
```
public int nextInt() {
   return next(32);
 }
```

Returns
`int`	the next pseudorandom, uniformly distributed `int` value from this random number generator's sequence

nextInt

Added in API level 1

public int nextInt (int bound)

Returns a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence. The general contract of nextInt is that one int value in the specified range is pseudorandomly generated and returned. All bound possible int values are produced with (approximately) equal probability.

Implementation Requirements:

The method nextInt(int bound) is implemented by class Random as if by:
```
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;
 }
```
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 int values from the stated range with perfect uniformity.
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.
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 low-order 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.

Parameters
`bound`	`int`: the upper bound (exclusive). Must be positive.

Returns
`int`	the next pseudorandom, uniformly distributed `int` value between zero (inclusive) and `bound` (exclusive) from this random number generator's sequence

Throws
`IllegalArgumentException`	if bound is not positive

nextLong

Added in API level 1

public long nextLong ()

Returns the next pseudorandom, uniformly distributed long value from this random number generator's sequence. The general contract of nextLong is that one long value is pseudorandomly generated and returned.

Implementation Requirements:

The method nextLong is implemented by class Random as if by:
```
public long nextLong() {
   return ((long)next(32) << 32) + next(32);
 }
```
Because class Random uses a seed with only 48 bits, this algorithm will not return all possible long values.

Returns
`long`	the next pseudorandom, uniformly distributed `long` value from this random number generator's sequence

setSeed

Added in API level 1

public void setSeed (long seed)

Sets or updates the seed of this random number generator using the provided long seed value (optional operation).

Implementation Requirements:

The implementation in this class alters the state of this random number generator so that it is in the same state as if it had just been created with new Random(seed). It atomically updates the seed to
```
(seed ^ 0x5DEECE66DL) & ((1L << 48) - 1)
```
and clears the haveNextNextGaussian flag used by nextGaussian(). Note that this uses only 48 bits of the given seed value.

Parameters
`seed`	`long`: the seed value

Throws
`UnsupportedOperationException`	if the `setSeed` operation is not supported by this random number generator

Protected methods

Added in API level 1

protected int next (int bits)

Generates the next pseudorandom number. This method returns an int value such that, if the argument bits is between 1 and 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 0 or 1.

API Note:

The other random-producing methods in this class are implemented in terms of this method, so subclasses can override just this method to provide a different source of pseudorandom numbers for the entire class.

Implementation Requirements:

The implementation in this class atomically updates the seed to
```
(seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)
```
and returns
```
(int)(seed >>> (48 - bits)).
```
This is a linear congruential pseudorandom number generator, as defined by D. H. Lehmer and described by Donald E. Knuth in The Art of Computer Programming, Volume 2, Third edition: Seminumerical Algorithms, section 3.2.1.

Parameters
`bits`	`int`: random bits

Returns
`int`	the next pseudorandom value from this random number generator's sequence