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/publicdomain/zero/1.0/
 */

/*
 * @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:	1.7
Committed:	Tue Mar 15 19:47:04 2011 UTC (13 years, 1 month ago) by jsr166
Branch:	MAIN
CVS Tags:	release-1_7_0
Changes since 1.6:	+1 -1 lines
Log Message:	Update Creative Commons license URL in legal notices
#	Content
1	/*
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/publicdomain/zero/1.0/
5	*/
6
7	/*
8	* @test
9	* @bug 4949279
10	* @summary Independent instantiations of Random() have distinct seeds.
11	*/
12
13	import java.util.Random;
14
15	public class DistinctSeeds {
16	public static void main(String[] args) throws Exception {
17	// 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	throw new RuntimeException("Random() seeds not unique.");
22	}
23	}