java.util.Random Class Reference

Public Member Functions
	Random ()
	Random (long seed)
boolean	nextBoolean ()
void	nextBytes (byte[] buf)
double	nextDouble ()
float	nextFloat ()
int	nextInt ()
int	nextInt (int n)
long	nextLong ()
synchronized void	setSeed (long seed)

Protected Member Functions
synchronized int	next (int bits)

Detailed Description

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.

See also

java.security.SecureRandom

Constructor & Destructor Documentation

Random() [1/2]

java.util.Random.Random ( )

inline

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.

Random() [2/2]

java.util.Random.Random ( long  seed )

inline

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.

Member Function Documentation

next()

synchronized int java.util.Random.next ( int  bits )

inlineprotected

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.

nextBoolean()

boolean java.util.Random.nextBoolean ( )

inline

Returns a pseudo-random uniformly distributed

boolean 

.

nextBytes()

void java.util.Random.nextBytes ( byte []  buf )

inline

Fills

buf 

with random bytes.

nextDouble()

double java.util.Random.nextDouble ( )

inline

Returns a pseudo-random uniformly distributed

double 

in the half-open range [0.0, 1.0).

nextFloat()

float java.util.Random.nextFloat ( )

inline

Returns a pseudo-random uniformly distributed

float 

in the half-open range [0.0, 1.0).

nextInt() [1/2]

int java.util.Random.nextInt ( )

inline

Returns a pseudo-random uniformly distributed

int 

.

nextInt() [2/2]

int java.util.Random.nextInt ( int  n )

inline

Returns a pseudo-random uniformly distributed

int 

in the half-open range [0, n).

nextLong()

long java.util.Random.nextLong ( )

inline

Returns a pseudo-random uniformly distributed

long 

.

setSeed()

synchronized void java.util.Random.setSeed ( long  seed )

inline

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

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The documentation for this class was generated from the following file:

• src/java/util/Random.java