util/Random/DistinctSeeds.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/licenses/publicdomain
 */

/*
 * @test
 * @bug 4949279
 * @summary Independent instantiations of Random() have distinct seeds.
 */

import java.util.Random;

public class DistinctSeeds {
    public static void main(String[] args) throws Exception {
        // Strictly speaking, it is possible for these to randomly fail,
        // but the probability should be *extremely* small (< 2**-63).
        if (new Random().nextLong() == new Random().nextLong() ||
            new Random().nextLong() == new Random().nextLong())
            throw new RuntimeException("Random() seeds not unique.");
    }
}
Revision:	1.6
Committed:	Mon Aug 31 22:24:46 2009 UTC (14 years, 8 months ago) by jsr166
Branch:	MAIN
Changes since 1.5:	+4 -4 lines
Log Message:	untabify
#	User	Rev	Content
1	dl	1.3	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/licenses/publicdomain
5			*/
6
7	jsr166	1.4	/*
8	jsr166	1.5	* @test
9	jsr166	1.4	* @bug 4949279
10			* @summary Independent instantiations of Random() have distinct seeds.
11			*/
12	dl	1.3
13	jsr166	1.1	import java.util.Random;
14
15			public class DistinctSeeds {
16			public static void main(String[] args) throws Exception {
17	jsr166	1.6	// Strictly speaking, it is possible for these to randomly fail,
18			// but the probability should be extremely small (< 2**-63).
19			if (new Random().nextLong() == new Random().nextLong() \|\|
20			new Random().nextLong() == new Random().nextLong())
21	jsr166	1.2	throw new RuntimeException("Random() seeds not unique.");
22	jsr166	1.1	}
23			}