DistinctSeeds.java revision 2352
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
*/
/*
* @test
* @bug 4949279 6937857
* @summary Independent instantiations of Random() have distinct seeds.
*/
public class DistinctSeeds {
// Strictly speaking, it is possible for these to randomly fail,
// but the probability should be small (approximately 2**-48).
throw new RuntimeException("Random() seeds not unique.");
// Now try generating seeds concurrently
class RandomCollector implements Runnable {
public void run() {
}
}
final int threadCount = 2;
for (int i = 0; i < threadCount; i++) {
RandomCollector r = new RandomCollector();
collectors.add(r);
}
int collisions = 0;
for (RandomCollector r : collectors) {
for (long x : r.randoms) {
if (s.contains(x))
collisions++;
s.add(x);
}
}
if (collisions > 10)
throw new Error("too many collisions");
}
}