Randomization - Data Structures and Problem Solving Using Java - page 400

1 private static final int A = 48271;
2 private static final int M = 2147483647;
3 private static final int Q = M / A;
4 private static final int R = M % A;
5
6 /**
7 * Construct this Random object with
8 * initial state obtained from system clock.
9 */
10 public Random( )
11 {
12 this( (int) ( System.nanoTime( ) % Integer.MAX_VALUE ) );
13 }
14
15 /**
16 * Construct this Random object with
17 * specified initial state
18 * @param initialValue the initial state.
19 */
20 public Random( int initialValue )
21 {
22 if( initialValue < 0 )
23 {
24 initialValue += M;
25 initialValue++;
26 }
27
28 state = initialValue;
29 if( state <= 0 )
30 state = 1;
31 }
32
33 /**
34 * Return a pseudorandom int, and change the
35 * internal state.
36 * @return the pseudorandom int.
37 */
38 public int nextInt( )
39 {
40 int tmpState = A * ( state % Q ) - R * ( state / Q );
41 if( tmpState >= 0 )
42 state = tmpState;
43 else
44 state = tmpState + M;
45
46 return state;
47 }
figure 9.2
Random number generator that works if INT_MAX is at least 2 31 -1