test/tck/ThreadLocalRandomTest.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/
 */

import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;

import junit.framework.Test;
import junit.framework.TestSuite;

public class ThreadLocalRandomTest extends JSR166TestCase {

    public static void main(String[] args) {
        main(suite(), args);
    }
    public static Test suite() {
        return new TestSuite(ThreadLocalRandomTest.class);
    }

    /*
     * Testing coverage notes:
     *
     * We don't test randomness properties, but only that repeated
     * calls, up to NCALLS tries, produce at least one different
     * result.  For bounded versions, we sample various intervals
     * across multiples of primes.
     */

    // max numbers of calls to detect getting stuck on one value
    static final int NCALLS = 10000;

    // max sampled int bound
    static final int MAX_INT_BOUND = (1 << 28);

    // max sampled long bound
    static final long MAX_LONG_BOUND = (1L << 42);

    // Number of replications for other checks
    static final int REPS = 20;

    /**
     * setSeed throws UnsupportedOperationException
     */
    public void testSetSeed() {
        try {
            ThreadLocalRandom.current().setSeed(17);
            shouldThrow();
        } catch (UnsupportedOperationException success) {}
    }

    /**
     * Repeated calls to next (only accessible via reflection) produce
     * at least two distinct results, and repeated calls produce all
     * possible values.
     */
    public void testNext() throws ReflectiveOperationException {
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        try {
            java.lang.reflect.Method m
                = ThreadLocalRandom.class.getDeclaredMethod(
                    "next", new Class[] { int.class });
            m.setAccessible(true);

            int i;
            {
                int val = new java.util.Random().nextInt(4);
                for (i = 0; i < NCALLS; i++) {
                    int q = (int) m.invoke(rnd, new Object[] { 2 });
                    if (val == q) break;
                }
                assertTrue(i < NCALLS);
            }

            {
                int r = (int) m.invoke(rnd, new Object[] { 3 });
                for (i = 0; i < NCALLS; i++) {
                    int q = (int) m.invoke(rnd, new Object[] { 3 });
                    assertTrue(q < (1<<3));
                    if (r != q) break;
                }
                assertTrue(i < NCALLS);
            }
        } catch (SecurityException acceptable) {}
    }

    /**
     * Repeated calls to nextInt produce at least two distinct results
     */
    public void testNextInt() {
        int f = ThreadLocalRandom.current().nextInt();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextInt() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * Repeated calls to nextLong produce at least two distinct results
     */
    public void testNextLong() {
        long f = ThreadLocalRandom.current().nextLong();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextLong() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * Repeated calls to nextBoolean produce at least two distinct results
     */
    public void testNextBoolean() {
        boolean f = ThreadLocalRandom.current().nextBoolean();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextBoolean() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * Repeated calls to nextFloat produce at least two distinct results
     */
    public void testNextFloat() {
        float f = ThreadLocalRandom.current().nextFloat();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextFloat() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * Repeated calls to nextDouble produce at least two distinct results
     */
    public void testNextDouble() {
        double f = ThreadLocalRandom.current().nextDouble();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextDouble() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * Repeated calls to nextGaussian produce at least two distinct results
     */
    public void testNextGaussian() {
        double f = ThreadLocalRandom.current().nextGaussian();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextGaussian() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * nextInt(non-positive) throws IllegalArgumentException
     */
    public void testNextIntBoundNonPositive() {
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        for (int bound : new int[] { 0, -17, Integer.MIN_VALUE }) {
            try {
                rnd.nextInt(bound);
                shouldThrow();
            } catch (IllegalArgumentException success) {}
        }
    }

    /**
     * nextInt(least >= bound) throws IllegalArgumentException
     */
    public void testNextIntBadBounds() {
        int[][] badBoundss = {
            { 17, 2 },
            { -42, -42 },
            { Integer.MAX_VALUE, Integer.MIN_VALUE },
        };
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        for (int[] badBounds : badBoundss) {
            try {
                rnd.nextInt(badBounds[0], badBounds[1]);
                shouldThrow();
            } catch (IllegalArgumentException success) {}
        }
    }

    /**
     * nextInt(bound) returns 0 <= value < bound;
     * repeated calls produce at least two distinct results
     */
    public void testNextIntBounded() {
        // sample bound space across prime number increments
        for (int bound = 2; bound < MAX_INT_BOUND; bound += 524959) {
            int f = ThreadLocalRandom.current().nextInt(bound);
            assertTrue(0 <= f && f < bound);
            int i = 0;
            int j;
            while (i < NCALLS &&
                   (j = ThreadLocalRandom.current().nextInt(bound)) == f) {
                assertTrue(0 <= j && j < bound);
                ++i;
            }
            assertTrue(i < NCALLS);
        }
    }

    /**
     * nextInt(least, bound) returns least <= value < bound;
     * repeated calls produce at least two distinct results
     */
    public void testNextIntBounded2() {
        for (int least = -15485863; least < MAX_INT_BOUND; least += 524959) {
            for (int bound = least + 2; bound > least && bound < MAX_INT_BOUND; bound += 49979687) {
                int f = ThreadLocalRandom.current().nextInt(least, bound);
                assertTrue(least <= f && f < bound);
                int i = 0;
                int j;
                while (i < NCALLS &&
                       (j = ThreadLocalRandom.current().nextInt(least, bound)) == f) {
                    assertTrue(least <= j && j < bound);
                    ++i;
                }
                assertTrue(i < NCALLS);
            }
        }
    }

    /**
     * nextLong(non-positive) throws IllegalArgumentException
     */
    public void testNextLongBoundNonPositive() {
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        for (long bound : new long[] { 0L, -17L, Long.MIN_VALUE }) {
            try {
                rnd.nextLong(bound);
                shouldThrow();
            } catch (IllegalArgumentException success) {}
        }
    }

    /**
     * nextLong(least >= bound) throws IllegalArgumentException
     */
    public void testNextLongBadBounds() {
        long[][] badBoundss = {
            { 17L, 2L },
            { -42L, -42L },
            { Long.MAX_VALUE, Long.MIN_VALUE },
        };
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        for (long[] badBounds : badBoundss) {
            try {
                rnd.nextLong(badBounds[0], badBounds[1]);
                shouldThrow();
            } catch (IllegalArgumentException success) {}
        }
    }

    /**
     * nextLong(bound) returns 0 <= value < bound;
     * repeated calls produce at least two distinct results
     */
    public void testNextLongBounded() {
        for (long bound = 2; bound < MAX_LONG_BOUND; bound += 15485863) {
            long f = ThreadLocalRandom.current().nextLong(bound);
            assertTrue(0 <= f && f < bound);
            int i = 0;
            long j;
            while (i < NCALLS &&
                   (j = ThreadLocalRandom.current().nextLong(bound)) == f) {
                assertTrue(0 <= j && j < bound);
                ++i;
            }
            assertTrue(i < NCALLS);
        }
    }

    /**
     * nextLong(least, bound) returns least <= value < bound;
     * repeated calls produce at least two distinct results
     */
    public void testNextLongBounded2() {
        for (long least = -86028121; least < MAX_LONG_BOUND; least += 982451653L) {
            for (long bound = least + 2; bound > least && bound < MAX_LONG_BOUND; bound += Math.abs(bound * 7919)) {
                long f = ThreadLocalRandom.current().nextLong(least, bound);
                assertTrue(least <= f && f < bound);
                int i = 0;
                long j;
                while (i < NCALLS &&
                       (j = ThreadLocalRandom.current().nextLong(least, bound)) == f) {
                    assertTrue(least <= j && j < bound);
                    ++i;
                }
                assertTrue(i < NCALLS);
            }
        }
    }

    /**
     * nextDouble(non-positive) throws IllegalArgumentException
     */
    public void testNextDoubleBoundNonPositive() {
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        double[] badBounds = {
            0.0d,
            -17.0d,
            -Double.MIN_VALUE,
            Double.NEGATIVE_INFINITY,
            Double.NaN,
        };
        for (double bound : badBounds) {
            try {
                rnd.nextDouble(bound);
                shouldThrow();
            } catch (IllegalArgumentException success) {}
        }
    }

    /**
     * nextDouble(least, bound) returns least <= value < bound;
     * repeated calls produce at least two distinct results
     */
    public void testNextDoubleBounded2() {
        for (double least = 0.0001; least < 1.0e20; least *= 8) {
            for (double bound = least * 1.001; bound < 1.0e20; bound *= 16) {
                double f = ThreadLocalRandom.current().nextDouble(least, bound);
                assertTrue(least <= f && f < bound);
                int i = 0;
                double j;
                while (i < NCALLS &&
                       (j = ThreadLocalRandom.current().nextDouble(least, bound)) == f) {
                    assertTrue(least <= j && j < bound);
                    ++i;
                }
                assertTrue(i < NCALLS);
            }
        }
    }

    /**
     * Different threads produce different pseudo-random sequences
     */
    public void testDifferentSequences() {
        // Don't use main thread's ThreadLocalRandom - it is likely to
        // be polluted by previous tests.
        final AtomicReference<ThreadLocalRandom> threadLocalRandom =
            new AtomicReference<ThreadLocalRandom>();
        final AtomicLong rand = new AtomicLong();

        long firstRand = 0;
        ThreadLocalRandom firstThreadLocalRandom = null;

        Runnable getRandomState = new CheckedRunnable() {
            public void realRun() {
                ThreadLocalRandom current = ThreadLocalRandom.current();
                assertSame(current, ThreadLocalRandom.current());
                // test bug: the following is not guaranteed and not true in JDK8
                //                assertNotSame(current, threadLocalRandom.get());
                rand.set(current.nextLong());
                threadLocalRandom.set(current);
            }};

        Thread first = newStartedThread(getRandomState);
        awaitTermination(first);
        firstRand = rand.get();
        firstThreadLocalRandom = threadLocalRandom.get();

        for (int i = 0; i < NCALLS; i++) {
            Thread t = newStartedThread(getRandomState);
            awaitTermination(t);
            if (firstRand != rand.get())
                return;
        }
        fail("all threads generate the same pseudo-random sequence");
    }

}
Revision:	1.22
Committed:	Sun Nov 13 03:36:50 2016 UTC (7 years, 6 months ago) by jsr166
Branch:	MAIN
Changes since 1.21:	+35 -0 lines
Log Message:	revise (uselessly inaccessible) next(int) method javadoc, implementation and tests
#	User	Rev	Content
1	dl	1.1	/*
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	jsr166	1.8	* http://creativecommons.org/publicdomain/zero/1.0/
5	dl	1.1	*/
6	jsr166	1.20
7	jsr166	1.10	import java.util.concurrent.ThreadLocalRandom;
8	jsr166	1.11	import java.util.concurrent.atomic.AtomicLong;
9			import java.util.concurrent.atomic.AtomicReference;
10	dl	1.1
11	jsr166	1.20	import junit.framework.Test;
12			import junit.framework.TestSuite;
13
14	dl	1.1	public class ThreadLocalRandomTest extends JSR166TestCase {
15
16			public static void main(String[] args) {
17	jsr166	1.21	main(suite(), args);
18	dl	1.1	}
19			public static Test suite() {
20	jsr166	1.4	return new TestSuite(ThreadLocalRandomTest.class);
21	dl	1.1	}
22
23	jsr166	1.13	/*
24	dl	1.1	* Testing coverage notes:
25	jsr166	1.2	*
26	dl	1.1	* We don't test randomness properties, but only that repeated
27			* calls, up to NCALLS tries, produce at least one different
28			* result. For bounded versions, we sample various intervals
29			* across multiples of primes.
30			*/
31
32	jsr166	1.14	// max numbers of calls to detect getting stuck on one value
33	dl	1.1	static final int NCALLS = 10000;
34
35			// max sampled int bound
36			static final int MAX_INT_BOUND = (1 << 28);
37
38	jsr166	1.14	// max sampled long bound
39	dl	1.1	static final long MAX_LONG_BOUND = (1L << 42);
40
41	dl	1.15	// Number of replications for other checks
42			static final int REPS = 20;
43
44	dl	1.1	/**
45			* setSeed throws UnsupportedOperationException
46			*/
47			public void testSetSeed() {
48			try {
49			ThreadLocalRandom.current().setSeed(17);
50	jsr166	1.3	shouldThrow();
51	jsr166	1.5	} catch (UnsupportedOperationException success) {}
52	dl	1.1	}
53
54			/**
55	jsr166	1.22	* Repeated calls to next (only accessible via reflection) produce
56			* at least two distinct results, and repeated calls produce all
57			* possible values.
58			*/
59			public void testNext() throws ReflectiveOperationException {
60			ThreadLocalRandom rnd = ThreadLocalRandom.current();
61			try {
62			java.lang.reflect.Method m
63			= ThreadLocalRandom.class.getDeclaredMethod(
64			"next", new Class[] { int.class });
65			m.setAccessible(true);
66
67			int i;
68			{
69			int val = new java.util.Random().nextInt(4);
70			for (i = 0; i < NCALLS; i++) {
71			int q = (int) m.invoke(rnd, new Object[] { 2 });
72			if (val == q) break;
73			}
74			assertTrue(i < NCALLS);
75			}
76
77			{
78			int r = (int) m.invoke(rnd, new Object[] { 3 });
79			for (i = 0; i < NCALLS; i++) {
80			int q = (int) m.invoke(rnd, new Object[] { 3 });
81			assertTrue(q < (1<<3));
82			if (r != q) break;
83			}
84			assertTrue(i < NCALLS);
85			}
86			} catch (SecurityException acceptable) {}
87			}
88
89			/**
90	jsr166	1.14	* Repeated calls to nextInt produce at least two distinct results
91	dl	1.1	*/
92			public void testNextInt() {
93			int f = ThreadLocalRandom.current().nextInt();
94			int i = 0;
95			while (i < NCALLS && ThreadLocalRandom.current().nextInt() == f)
96			++i;
97			assertTrue(i < NCALLS);
98			}
99
100			/**
101	jsr166	1.14	* Repeated calls to nextLong produce at least two distinct results
102	dl	1.1	*/
103			public void testNextLong() {
104			long f = ThreadLocalRandom.current().nextLong();
105			int i = 0;
106			while (i < NCALLS && ThreadLocalRandom.current().nextLong() == f)
107			++i;
108			assertTrue(i < NCALLS);
109			}
110
111			/**
112	jsr166	1.14	* Repeated calls to nextBoolean produce at least two distinct results
113	dl	1.1	*/
114			public void testNextBoolean() {
115			boolean f = ThreadLocalRandom.current().nextBoolean();
116			int i = 0;
117			while (i < NCALLS && ThreadLocalRandom.current().nextBoolean() == f)
118			++i;
119			assertTrue(i < NCALLS);
120			}
121
122			/**
123	jsr166	1.14	* Repeated calls to nextFloat produce at least two distinct results
124	dl	1.1	*/
125			public void testNextFloat() {
126			float f = ThreadLocalRandom.current().nextFloat();
127			int i = 0;
128			while (i < NCALLS && ThreadLocalRandom.current().nextFloat() == f)
129			++i;
130			assertTrue(i < NCALLS);
131			}
132
133			/**
134	jsr166	1.14	* Repeated calls to nextDouble produce at least two distinct results
135	dl	1.1	*/
136			public void testNextDouble() {
137			double f = ThreadLocalRandom.current().nextDouble();
138	jsr166	1.14	int i = 0;
139	dl	1.1	while (i < NCALLS && ThreadLocalRandom.current().nextDouble() == f)
140			++i;
141			assertTrue(i < NCALLS);
142			}
143
144			/**
145	jsr166	1.14	* Repeated calls to nextGaussian produce at least two distinct results
146	dl	1.1	*/
147			public void testNextGaussian() {
148			double f = ThreadLocalRandom.current().nextGaussian();
149			int i = 0;
150			while (i < NCALLS && ThreadLocalRandom.current().nextGaussian() == f)
151			++i;
152			assertTrue(i < NCALLS);
153			}
154
155			/**
156	jsr166	1.19	* nextInt(non-positive) throws IllegalArgumentException
157	dl	1.1	*/
158	jsr166	1.19	public void testNextIntBoundNonPositive() {
159			ThreadLocalRandom rnd = ThreadLocalRandom.current();
160			for (int bound : new int[] { 0, -17, Integer.MIN_VALUE }) {
161			try {
162			rnd.nextInt(bound);
163			shouldThrow();
164			} catch (IllegalArgumentException success) {}
165			}
166	dl	1.1	}
167
168			/**
169	jsr166	1.14	* nextInt(least >= bound) throws IllegalArgumentException
170	dl	1.1	*/
171			public void testNextIntBadBounds() {
172	jsr166	1.19	int[][] badBoundss = {
173			{ 17, 2 },
174			{ -42, -42 },
175			{ Integer.MAX_VALUE, Integer.MIN_VALUE },
176			};
177			ThreadLocalRandom rnd = ThreadLocalRandom.current();
178			for (int[] badBounds : badBoundss) {
179			try {
180			rnd.nextInt(badBounds[0], badBounds[1]);
181			shouldThrow();
182			} catch (IllegalArgumentException success) {}
183			}
184	dl	1.1	}
185
186			/**
187			* nextInt(bound) returns 0 <= value < bound;
188	jsr166	1.14	* repeated calls produce at least two distinct results
189	dl	1.1	*/
190			public void testNextIntBounded() {
191			// sample bound space across prime number increments
192			for (int bound = 2; bound < MAX_INT_BOUND; bound += 524959) {
193			int f = ThreadLocalRandom.current().nextInt(bound);
194			assertTrue(0 <= f && f < bound);
195			int i = 0;
196			int j;
197	jsr166	1.2	while (i < NCALLS &&
198	dl	1.1	(j = ThreadLocalRandom.current().nextInt(bound)) == f) {
199			assertTrue(0 <= j && j < bound);
200			++i;
201			}
202			assertTrue(i < NCALLS);
203			}
204			}
205
206			/**
207			* nextInt(least, bound) returns least <= value < bound;
208	jsr166	1.14	* repeated calls produce at least two distinct results
209	dl	1.1	*/
210			public void testNextIntBounded2() {
211			for (int least = -15485863; least < MAX_INT_BOUND; least += 524959) {
212			for (int bound = least + 2; bound > least && bound < MAX_INT_BOUND; bound += 49979687) {
213			int f = ThreadLocalRandom.current().nextInt(least, bound);
214			assertTrue(least <= f && f < bound);
215			int i = 0;
216			int j;
217	jsr166	1.2	while (i < NCALLS &&
218	dl	1.1	(j = ThreadLocalRandom.current().nextInt(least, bound)) == f) {
219			assertTrue(least <= j && j < bound);
220			++i;
221			}
222			assertTrue(i < NCALLS);
223			}
224			}
225			}
226
227			/**
228	jsr166	1.19	* nextLong(non-positive) throws IllegalArgumentException
229	dl	1.1	*/
230	jsr166	1.19	public void testNextLongBoundNonPositive() {
231			ThreadLocalRandom rnd = ThreadLocalRandom.current();
232			for (long bound : new long[] { 0L, -17L, Long.MIN_VALUE }) {
233			try {
234			rnd.nextLong(bound);
235			shouldThrow();
236			} catch (IllegalArgumentException success) {}
237			}
238	dl	1.1	}
239
240			/**
241	jsr166	1.14	* nextLong(least >= bound) throws IllegalArgumentException
242	dl	1.1	*/
243			public void testNextLongBadBounds() {
244	jsr166	1.19	long[][] badBoundss = {
245			{ 17L, 2L },
246			{ -42L, -42L },
247			{ Long.MAX_VALUE, Long.MIN_VALUE },
248			};
249			ThreadLocalRandom rnd = ThreadLocalRandom.current();
250			for (long[] badBounds : badBoundss) {
251			try {
252			rnd.nextLong(badBounds[0], badBounds[1]);
253			shouldThrow();
254			} catch (IllegalArgumentException success) {}
255			}
256	dl	1.1	}
257
258			/**
259			* nextLong(bound) returns 0 <= value < bound;
260	jsr166	1.14	* repeated calls produce at least two distinct results
261	dl	1.1	*/
262			public void testNextLongBounded() {
263			for (long bound = 2; bound < MAX_LONG_BOUND; bound += 15485863) {
264			long f = ThreadLocalRandom.current().nextLong(bound);
265			assertTrue(0 <= f && f < bound);
266			int i = 0;
267			long j;
268	jsr166	1.2	while (i < NCALLS &&
269	dl	1.1	(j = ThreadLocalRandom.current().nextLong(bound)) == f) {
270			assertTrue(0 <= j && j < bound);
271			++i;
272			}
273			assertTrue(i < NCALLS);
274			}
275			}
276
277			/**
278			* nextLong(least, bound) returns least <= value < bound;
279	jsr166	1.14	* repeated calls produce at least two distinct results
280	dl	1.1	*/
281			public void testNextLongBounded2() {
282			for (long least = -86028121; least < MAX_LONG_BOUND; least += 982451653L) {
283			for (long bound = least + 2; bound > least && bound < MAX_LONG_BOUND; bound += Math.abs(bound * 7919)) {
284			long f = ThreadLocalRandom.current().nextLong(least, bound);
285			assertTrue(least <= f && f < bound);
286			int i = 0;
287			long j;
288	jsr166	1.2	while (i < NCALLS &&
289	dl	1.1	(j = ThreadLocalRandom.current().nextLong(least, bound)) == f) {
290			assertTrue(least <= j && j < bound);
291			++i;
292			}
293			assertTrue(i < NCALLS);
294			}
295			}
296			}
297
298			/**
299	jsr166	1.19	* nextDouble(non-positive) throws IllegalArgumentException
300			*/
301			public void testNextDoubleBoundNonPositive() {
302			ThreadLocalRandom rnd = ThreadLocalRandom.current();
303			double[] badBounds = {
304			0.0d,
305			-17.0d,
306			-Double.MIN_VALUE,
307			Double.NEGATIVE_INFINITY,
308			Double.NaN,
309			};
310			for (double bound : badBounds) {
311			try {
312			rnd.nextDouble(bound);
313			shouldThrow();
314			} catch (IllegalArgumentException success) {}
315			}
316			}
317
318			/**
319	dl	1.1	* nextDouble(least, bound) returns least <= value < bound;
320	jsr166	1.14	* repeated calls produce at least two distinct results
321	dl	1.1	*/
322			public void testNextDoubleBounded2() {
323			for (double least = 0.0001; least < 1.0e20; least *= 8) {
324			for (double bound = least * 1.001; bound < 1.0e20; bound *= 16) {
325			double f = ThreadLocalRandom.current().nextDouble(least, bound);
326			assertTrue(least <= f && f < bound);
327			int i = 0;
328			double j;
329	jsr166	1.2	while (i < NCALLS &&
330	dl	1.1	(j = ThreadLocalRandom.current().nextDouble(least, bound)) == f) {
331			assertTrue(least <= j && j < bound);
332			++i;
333			}
334			assertTrue(i < NCALLS);
335			}
336			}
337			}
338
339	jsr166	1.11	/**
340			* Different threads produce different pseudo-random sequences
341			*/
342			public void testDifferentSequences() {
343			// Don't use main thread's ThreadLocalRandom - it is likely to
344			// be polluted by previous tests.
345			final AtomicReference<ThreadLocalRandom> threadLocalRandom =
346			new AtomicReference<ThreadLocalRandom>();
347			final AtomicLong rand = new AtomicLong();
348
349			long firstRand = 0;
350			ThreadLocalRandom firstThreadLocalRandom = null;
351
352	jsr166	1.18	Runnable getRandomState = new CheckedRunnable() {
353	jsr166	1.11	public void realRun() {
354			ThreadLocalRandom current = ThreadLocalRandom.current();
355			assertSame(current, ThreadLocalRandom.current());
356	dl	1.12	// test bug: the following is not guaranteed and not true in JDK8
357			// assertNotSame(current, threadLocalRandom.get());
358	jsr166	1.11	rand.set(current.nextLong());
359			threadLocalRandom.set(current);
360			}};
361
362			Thread first = newStartedThread(getRandomState);
363			awaitTermination(first);
364			firstRand = rand.get();
365			firstThreadLocalRandom = threadLocalRandom.get();
366
367			for (int i = 0; i < NCALLS; i++) {
368			Thread t = newStartedThread(getRandomState);
369			awaitTermination(t);
370			if (firstRand != rand.get())
371			return;
372			}
373			fail("all threads generate the same pseudo-random sequence");
374			}
375
376	dl	1.1	}