21.9

java.util.Random

THE PACKAGE JAVA.UTIL

21.9.7

protected int next(int bits)

The general contract of

next

 is that it returns an

int

 value and 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

.

The method

next

 is implemented by class

Random

 as follows:

synchronized protected int next(int bits) {

seed = (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48)   1);

return (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:

Seminumerical Algorithms

, section 3.2.1.

21.9.8

public int nextInt()

The general contract of

nextInt

 is that one

int

 value is pseudorandomly gener 

ated and returned. All 2

32

possible

int

 values are produced with (approximately)

equal probability.

The method

setSeed

 is implemented by class

Random

 as follows:

public int nextInt() {  return next(32); }

21.9.9

public long nextLong()

The general contract of

nextLong

 is that one

long

 value is pseudorandomly gen 

erated and returned. All 2

64

possible

long

 values are produced with (approxi 

mately) equal probability.

The method

setSeed

 is implemented by class

Random

 as follows:

public long nextLong() {

return ((long)next(32) << 32) + next(32);

}

648