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Summary: Ctors | Methods | Protected Methods | Inherited Methods | [Expand All]

Added in API level 1

public class

Random

extends Object
implements Serializable

java.lang.Object
↳	java.util.Random

Known Direct Subclasses

SecureRandom

Class Overview

This class provides methods that return pseudo-random values.

It is dangerous to seed Random with the current time because that value is more predictable to an attacker than the default seed.

This class is thread-safe.

Summary

Public Constructors
	Random() Constructs a random generator with an initial state that is unlikely to be duplicated by a subsequent instantiation.
	Random(long seed) Construct a random generator with the given `seed` as the initial state.

Public Methods
boolean	nextBoolean() Returns a pseudo-random uniformly distributed `boolean`.
void	nextBytes(byte[] buf) Fills `buf` with random bytes.
double	nextDouble() Returns a pseudo-random uniformly distributed `double` in the half-open range [0.0, 1.0).
float	nextFloat() Returns a pseudo-random uniformly distributed `float` in the half-open range [0.0, 1.0).
synchronized double	nextGaussian() Returns a pseudo-random (approximately) normally distributed `double` with mean 0.0 and standard deviation 1.0.
int	nextInt(int n) Returns a pseudo-random uniformly distributed `int` in the half-open range [0, n).
int	nextInt() Returns a pseudo-random uniformly distributed `int`.
long	nextLong() Returns a pseudo-random uniformly distributed `long`.
synchronized void	setSeed(long seed) Modifies the seed using a linear congruential formula presented in The Art of Computer Programming, Volume 2, Section 3.2.1.

Protected Methods
synchronized int	next(int bits) Returns a pseudo-random uniformly distributed `int` value of the number of bits specified by the argument `bits` as described by Donald E.

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Inherited Methods

From class java.lang.Object

Object	clone() Creates and returns a copy of this `Object`.
boolean	equals(Object o) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of `Class` that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object.
final void	wait(long millis, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.
final void	wait(long millis) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.

Public Constructors

public Random ()

Added in API level 1

Constructs a random generator with an initial state that is unlikely to be duplicated by a subsequent instantiation.

The initial state (that is, the seed) is partially based on the current time of day in milliseconds.

public Random (long seed)

Added in API level 1

Construct a random generator with the given seed as the initial state. Equivalent to Random r = new Random(); r.setSeed(seed);.

This constructor is mainly useful for predictability in tests. The default constructor is likely to provide better randomness.

Public Methods

public boolean nextBoolean ()

Added in API level 1

Returns a pseudo-random uniformly distributed boolean.

public void nextBytes (byte[] buf)

Added in API level 1

Fills buf with random bytes.

public double nextDouble ()

Added in API level 1

Returns a pseudo-random uniformly distributed double in the half-open range [0.0, 1.0).

public float nextFloat ()

Added in API level 1

Returns a pseudo-random uniformly distributed float in the half-open range [0.0, 1.0).

public synchronized double nextGaussian ()

Added in API level 1

Returns a pseudo-random (approximately) normally distributed double with mean 0.0 and standard deviation 1.0. This method 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: Seminumerical Algorithms, section 3.4.1, subsection C, algorithm P.

public int nextInt (int n)

Added in API level 1

Returns a pseudo-random uniformly distributed int in the half-open range [0, n).

public int nextInt ()

Added in API level 1

Returns a pseudo-random uniformly distributed int.

public long nextLong ()

Added in API level 1

Returns a pseudo-random uniformly distributed long.

public synchronized void setSeed (long seed)

Added in API level 1

Modifies the seed using a linear congruential formula presented in The Art of Computer Programming, Volume 2, Section 3.2.1.

Protected Methods

protected synchronized int next (int bits)

Added in API level 1

Returns a pseudo-random uniformly distributed int value of the number of bits specified by the argument bits as described by Donald E. Knuth in The Art of Computer Programming, Volume 2: Seminumerical Algorithms, section 3.2.1.

Most applications will want to use one of this class' convenience methods instead.

Results

Interfaces

Classes

Enums

Exceptions

Errors

Random

Class Overview

See Also

Summary

Public Constructors

public Random ()

public Random (long seed)

Public Methods

public boolean nextBoolean ()

public void nextBytes (byte[] buf)

public double nextDouble ()

public float nextFloat ()

public synchronized double nextGaussian ()

public int nextInt (int n)

public int nextInt ()

public long nextLong ()

public synchronized void setSeed (long seed)

Protected Methods

protected synchronized int next (int bits)