Use java.lang.Math.random( )
to generate random numbers. There is no
claim that the random values it returns are very
good random numbers, however. This code
exercises the random( )
method:
// Random1.java // java.lang.Math.random( ) is static, don't need to construct Math System.out.println("A random from java.lang.Math is " + Math.random( ));
Note that this method only generates double values. If you need integers, you need to scale and round:
/** Generate random ints by scaling from Math.random( ). * Prints a series of 100 random integers from 1 to 10, inclusive. */ public class RandomInt { public static void main(String[] a) { for (int i=0; i<100; i++) System.out.println(1+(int)(Math.random( ) * 10)); } }
Section 5.14 is an easier way to get random integers.
Also see the Javadoc documentation for
java.lang.Math
, and the warning in this
chapter’s Introduction about pseudo-randomness versus real
randomness.
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