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 {
        // Inhibit "An illegal reflective access operation has occurred"
        if (!testImplementationDetails) return;

        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        final java.lang.reflect.Method m;
        try {
            m = ThreadLocalRandom.class.getDeclaredMethod(
                    "next", new Class[] { int.class });
            m.setAccessible(true);
        } catch (SecurityException acceptable) {
            // Security manager may deny access
            return;
        } catch (Exception ex) {
            // jdk9 module system may deny access
            if (ex.getClass().getSimpleName()
                .equals("InaccessibleObjectException"))
                return;
            throw ex;
        }

        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);
        }
    }

    /**
     * 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:	1.25
Committed:	Tue Sep 19 20:10:49 2017 UTC (6 years, 7 months ago) by jsr166
Branch:	MAIN
Changes since 1.24:	+3 -0 lines
Log Message:	Inhibit "An illegal reflective access operation has occurred"
#	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	import java.util.concurrent.ThreadLocalRandom;
8	import java.util.concurrent.atomic.AtomicLong;
9	import java.util.concurrent.atomic.AtomicReference;
10
11	import junit.framework.Test;
12	import junit.framework.TestSuite;
13
14	public class ThreadLocalRandomTest extends JSR166TestCase {
15
16	public static void main(String[] args) {
17	main(suite(), args);
18	}
19	public static Test suite() {
20	return new TestSuite(ThreadLocalRandomTest.class);
21	}
22
23	/*
24	* Testing coverage notes:
25	*
26	* 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	// max numbers of calls to detect getting stuck on one value
33	static final int NCALLS = 10000;
34
35	// max sampled int bound
36	static final int MAX_INT_BOUND = (1 << 28);
37
38	// max sampled long bound
39	static final long MAX_LONG_BOUND = (1L << 42);
40
41	// Number of replications for other checks
42	static final int REPS = 20;
43
44	/**
45	* setSeed throws UnsupportedOperationException
46	*/
47	public void testSetSeed() {
48	try {
49	ThreadLocalRandom.current().setSeed(17);
50	shouldThrow();
51	} catch (UnsupportedOperationException success) {}
52	}
53
54	/**
55	* 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	// Inhibit "An illegal reflective access operation has occurred"
61	if (!testImplementationDetails) return;
62
63	ThreadLocalRandom rnd = ThreadLocalRandom.current();
64	final java.lang.reflect.Method m;
65	try {
66	m = ThreadLocalRandom.class.getDeclaredMethod(
67	"next", new Class[] { int.class });
68	m.setAccessible(true);
69	} catch (SecurityException acceptable) {
70	// Security manager may deny access
71	return;
72	} catch (Exception ex) {
73	// jdk9 module system may deny access
74	if (ex.getClass().getSimpleName()
75	.equals("InaccessibleObjectException"))
76	return;
77	throw ex;
78	}
79
80	int i;
81	{
82	int val = new java.util.Random().nextInt(4);
83	for (i = 0; i < NCALLS; i++) {
84	int q = (int) m.invoke(rnd, new Object[] { 2 });
85	if (val == q) break;
86	}
87	assertTrue(i < NCALLS);
88	}
89
90	{
91	int r = (int) m.invoke(rnd, new Object[] { 3 });
92	for (i = 0; i < NCALLS; i++) {
93	int q = (int) m.invoke(rnd, new Object[] { 3 });
94	assertTrue(q < (1<<3));
95	if (r != q) break;
96	}
97	assertTrue(i < NCALLS);
98	}
99	}
100
101	/**
102	* Repeated calls to nextInt produce at least two distinct results
103	*/
104	public void testNextInt() {
105	int f = ThreadLocalRandom.current().nextInt();
106	int i = 0;
107	while (i < NCALLS && ThreadLocalRandom.current().nextInt() == f)
108	++i;
109	assertTrue(i < NCALLS);
110	}
111
112	/**
113	* Repeated calls to nextLong produce at least two distinct results
114	*/
115	public void testNextLong() {
116	long f = ThreadLocalRandom.current().nextLong();
117	int i = 0;
118	while (i < NCALLS && ThreadLocalRandom.current().nextLong() == f)
119	++i;
120	assertTrue(i < NCALLS);
121	}
122
123	/**
124	* Repeated calls to nextBoolean produce at least two distinct results
125	*/
126	public void testNextBoolean() {
127	boolean f = ThreadLocalRandom.current().nextBoolean();
128	int i = 0;
129	while (i < NCALLS && ThreadLocalRandom.current().nextBoolean() == f)
130	++i;
131	assertTrue(i < NCALLS);
132	}
133
134	/**
135	* Repeated calls to nextFloat produce at least two distinct results
136	*/
137	public void testNextFloat() {
138	float f = ThreadLocalRandom.current().nextFloat();
139	int i = 0;
140	while (i < NCALLS && ThreadLocalRandom.current().nextFloat() == f)
141	++i;
142	assertTrue(i < NCALLS);
143	}
144
145	/**
146	* Repeated calls to nextDouble produce at least two distinct results
147	*/
148	public void testNextDouble() {
149	double f = ThreadLocalRandom.current().nextDouble();
150	int i = 0;
151	while (i < NCALLS && ThreadLocalRandom.current().nextDouble() == f)
152	++i;
153	assertTrue(i < NCALLS);
154	}
155
156	/**
157	* Repeated calls to nextGaussian produce at least two distinct results
158	*/
159	public void testNextGaussian() {
160	double f = ThreadLocalRandom.current().nextGaussian();
161	int i = 0;
162	while (i < NCALLS && ThreadLocalRandom.current().nextGaussian() == f)
163	++i;
164	assertTrue(i < NCALLS);
165	}
166
167	/**
168	* nextInt(non-positive) throws IllegalArgumentException
169	*/
170	public void testNextIntBoundNonPositive() {
171	ThreadLocalRandom rnd = ThreadLocalRandom.current();
172	for (int bound : new int[] { 0, -17, Integer.MIN_VALUE }) {
173	try {
174	rnd.nextInt(bound);
175	shouldThrow();
176	} catch (IllegalArgumentException success) {}
177	}
178	}
179
180	/**
181	* nextInt(least >= bound) throws IllegalArgumentException
182	*/
183	public void testNextIntBadBounds() {
184	int[][] badBoundss = {
185	{ 17, 2 },
186	{ -42, -42 },
187	{ Integer.MAX_VALUE, Integer.MIN_VALUE },
188	};
189	ThreadLocalRandom rnd = ThreadLocalRandom.current();
190	for (int[] badBounds : badBoundss) {
191	try {
192	rnd.nextInt(badBounds[0], badBounds[1]);
193	shouldThrow();
194	} catch (IllegalArgumentException success) {}
195	}
196	}
197
198	/**
199	* nextInt(bound) returns 0 <= value < bound;
200	* repeated calls produce at least two distinct results
201	*/
202	public void testNextIntBounded() {
203	// sample bound space across prime number increments
204	for (int bound = 2; bound < MAX_INT_BOUND; bound += 524959) {
205	int f = ThreadLocalRandom.current().nextInt(bound);
206	assertTrue(0 <= f && f < bound);
207	int i = 0;
208	int j;
209	while (i < NCALLS &&
210	(j = ThreadLocalRandom.current().nextInt(bound)) == f) {
211	assertTrue(0 <= j && j < bound);
212	++i;
213	}
214	assertTrue(i < NCALLS);
215	}
216	}
217
218	/**
219	* nextInt(least, bound) returns least <= value < bound;
220	* repeated calls produce at least two distinct results
221	*/
222	public void testNextIntBounded2() {
223	for (int least = -15485863; least < MAX_INT_BOUND; least += 524959) {
224	for (int bound = least + 2; bound > least && bound < MAX_INT_BOUND; bound += 49979687) {
225	int f = ThreadLocalRandom.current().nextInt(least, bound);
226	assertTrue(least <= f && f < bound);
227	int i = 0;
228	int j;
229	while (i < NCALLS &&
230	(j = ThreadLocalRandom.current().nextInt(least, bound)) == f) {
231	assertTrue(least <= j && j < bound);
232	++i;
233	}
234	assertTrue(i < NCALLS);
235	}
236	}
237	}
238
239	/**
240	* nextLong(non-positive) throws IllegalArgumentException
241	*/
242	public void testNextLongBoundNonPositive() {
243	ThreadLocalRandom rnd = ThreadLocalRandom.current();
244	for (long bound : new long[] { 0L, -17L, Long.MIN_VALUE }) {
245	try {
246	rnd.nextLong(bound);
247	shouldThrow();
248	} catch (IllegalArgumentException success) {}
249	}
250	}
251
252	/**
253	* nextLong(least >= bound) throws IllegalArgumentException
254	*/
255	public void testNextLongBadBounds() {
256	long[][] badBoundss = {
257	{ 17L, 2L },
258	{ -42L, -42L },
259	{ Long.MAX_VALUE, Long.MIN_VALUE },
260	};
261	ThreadLocalRandom rnd = ThreadLocalRandom.current();
262	for (long[] badBounds : badBoundss) {
263	try {
264	rnd.nextLong(badBounds[0], badBounds[1]);
265	shouldThrow();
266	} catch (IllegalArgumentException success) {}
267	}
268	}
269
270	/**
271	* nextLong(bound) returns 0 <= value < bound;
272	* repeated calls produce at least two distinct results
273	*/
274	public void testNextLongBounded() {
275	for (long bound = 2; bound < MAX_LONG_BOUND; bound += 15485863) {
276	long f = ThreadLocalRandom.current().nextLong(bound);
277	assertTrue(0 <= f && f < bound);
278	int i = 0;
279	long j;
280	while (i < NCALLS &&
281	(j = ThreadLocalRandom.current().nextLong(bound)) == f) {
282	assertTrue(0 <= j && j < bound);
283	++i;
284	}
285	assertTrue(i < NCALLS);
286	}
287	}
288
289	/**
290	* nextLong(least, bound) returns least <= value < bound;
291	* repeated calls produce at least two distinct results
292	*/
293	public void testNextLongBounded2() {
294	for (long least = -86028121; least < MAX_LONG_BOUND; least += 982451653L) {
295	for (long bound = least + 2; bound > least && bound < MAX_LONG_BOUND; bound += Math.abs(bound * 7919)) {
296	long f = ThreadLocalRandom.current().nextLong(least, bound);
297	assertTrue(least <= f && f < bound);
298	int i = 0;
299	long j;
300	while (i < NCALLS &&
301	(j = ThreadLocalRandom.current().nextLong(least, bound)) == f) {
302	assertTrue(least <= j && j < bound);
303	++i;
304	}
305	assertTrue(i < NCALLS);
306	}
307	}
308	}
309
310	/**
311	* nextDouble(non-positive) throws IllegalArgumentException
312	*/
313	public void testNextDoubleBoundNonPositive() {
314	ThreadLocalRandom rnd = ThreadLocalRandom.current();
315	double[] badBounds = {
316	0.0d,
317	-17.0d,
318	-Double.MIN_VALUE,
319	Double.NEGATIVE_INFINITY,
320	Double.NaN,
321	};
322	for (double bound : badBounds) {
323	try {
324	rnd.nextDouble(bound);
325	shouldThrow();
326	} catch (IllegalArgumentException success) {}
327	}
328	}
329
330	/**
331	* nextDouble(least, bound) returns least <= value < bound;
332	* repeated calls produce at least two distinct results
333	*/
334	public void testNextDoubleBounded2() {
335	for (double least = 0.0001; least < 1.0e20; least *= 8) {
336	for (double bound = least * 1.001; bound < 1.0e20; bound *= 16) {
337	double f = ThreadLocalRandom.current().nextDouble(least, bound);
338	assertTrue(least <= f && f < bound);
339	int i = 0;
340	double j;
341	while (i < NCALLS &&
342	(j = ThreadLocalRandom.current().nextDouble(least, bound)) == f) {
343	assertTrue(least <= j && j < bound);
344	++i;
345	}
346	assertTrue(i < NCALLS);
347	}
348	}
349	}
350
351	/**
352	* Different threads produce different pseudo-random sequences
353	*/
354	public void testDifferentSequences() {
355	// Don't use main thread's ThreadLocalRandom - it is likely to
356	// be polluted by previous tests.
357	final AtomicReference<ThreadLocalRandom> threadLocalRandom =
358	new AtomicReference<ThreadLocalRandom>();
359	final AtomicLong rand = new AtomicLong();
360
361	long firstRand = 0;
362	ThreadLocalRandom firstThreadLocalRandom = null;
363
364	Runnable getRandomState = new CheckedRunnable() {
365	public void realRun() {
366	ThreadLocalRandom current = ThreadLocalRandom.current();
367	assertSame(current, ThreadLocalRandom.current());
368	// test bug: the following is not guaranteed and not true in JDK8
369	// assertNotSame(current, threadLocalRandom.get());
370	rand.set(current.nextLong());
371	threadLocalRandom.set(current);
372	}};
373
374	Thread first = newStartedThread(getRandomState);
375	awaitTermination(first);
376	firstRand = rand.get();
377	firstThreadLocalRandom = threadLocalRandom.get();
378
379	for (int i = 0; i < NCALLS; i++) {
380	Thread t = newStartedThread(getRandomState);
381	awaitTermination(t);
382	if (firstRand != rand.get())
383	return;
384	}
385	fail("all threads generate the same pseudo-random sequence");
386	}
387
388	}