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");
    }

    /**
     * Repeated calls to nextBytes produce at least values of different signs for every byte
     */
    public void testNextBytes() {
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        int n = rnd.nextInt(20);
        byte[] bytes = new byte[n];
        outer:
        for (int i = 0; i < n; i++) {
            for (int tries = NCALLS; tries-->0; ) {
                byte before = bytes[i];
                rnd.nextBytes(bytes);
                byte after = bytes[i];
                if (after * before < 0)
                    continue outer;
            }
            fail("not enough variation in random bytes");
        }
    }

}
Revision:	1.26
Committed:	Tue Oct 3 22:27:04 2017 UTC (6 years, 7 months ago) by jsr166
Branch:	MAIN
Changes since 1.25:	+20 -0 lines
Log Message:	8188047: Add SplittableRandom.nextBytes
#	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	jsr166	1.25	// Inhibit "An illegal reflective access operation has occurred"
61			if (!testImplementationDetails) return;
62
63	jsr166	1.22	ThreadLocalRandom rnd = ThreadLocalRandom.current();
64	jsr166	1.23	final java.lang.reflect.Method m;
65	jsr166	1.22	try {
66	jsr166	1.23	m = ThreadLocalRandom.class.getDeclaredMethod(
67	jsr166	1.22	"next", new Class[] { int.class });
68			m.setAccessible(true);
69	jsr166	1.24	} catch (SecurityException acceptable) {
70			// Security manager may deny access
71	jsr166	1.23	return;
72	jsr166	1.24	} catch (Exception ex) {
73			// jdk9 module system may deny access
74			if (ex.getClass().getSimpleName()
75			.equals("InaccessibleObjectException"))
76			return;
77			throw ex;
78	jsr166	1.23	}
79	jsr166	1.22
80	jsr166	1.23	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	jsr166	1.22	}
87	jsr166	1.23	assertTrue(i < NCALLS);
88			}
89	jsr166	1.22
90	jsr166	1.23	{
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	jsr166	1.22	}
97	jsr166	1.23	assertTrue(i < NCALLS);
98			}
99	jsr166	1.22	}
100
101			/**
102	jsr166	1.14	* Repeated calls to nextInt produce at least two distinct results
103	dl	1.1	*/
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	jsr166	1.14	* Repeated calls to nextLong produce at least two distinct results
114	dl	1.1	*/
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	jsr166	1.14	* Repeated calls to nextBoolean produce at least two distinct results
125	dl	1.1	*/
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	jsr166	1.14	* Repeated calls to nextFloat produce at least two distinct results
136	dl	1.1	*/
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	jsr166	1.14	* Repeated calls to nextDouble produce at least two distinct results
147	dl	1.1	*/
148			public void testNextDouble() {
149			double f = ThreadLocalRandom.current().nextDouble();
150	jsr166	1.14	int i = 0;
151	dl	1.1	while (i < NCALLS && ThreadLocalRandom.current().nextDouble() == f)
152			++i;
153			assertTrue(i < NCALLS);
154			}
155
156			/**
157	jsr166	1.14	* Repeated calls to nextGaussian produce at least two distinct results
158	dl	1.1	*/
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	jsr166	1.19	* nextInt(non-positive) throws IllegalArgumentException
169	dl	1.1	*/
170	jsr166	1.19	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	dl	1.1	}
179
180			/**
181	jsr166	1.14	* nextInt(least >= bound) throws IllegalArgumentException
182	dl	1.1	*/
183			public void testNextIntBadBounds() {
184	jsr166	1.19	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	dl	1.1	}
197
198			/**
199			* nextInt(bound) returns 0 <= value < bound;
200	jsr166	1.14	* repeated calls produce at least two distinct results
201	dl	1.1	*/
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	jsr166	1.2	while (i < NCALLS &&
210	dl	1.1	(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	jsr166	1.14	* repeated calls produce at least two distinct results
221	dl	1.1	*/
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	jsr166	1.2	while (i < NCALLS &&
230	dl	1.1	(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	jsr166	1.19	* nextLong(non-positive) throws IllegalArgumentException
241	dl	1.1	*/
242	jsr166	1.19	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	dl	1.1	}
251
252			/**
253	jsr166	1.14	* nextLong(least >= bound) throws IllegalArgumentException
254	dl	1.1	*/
255			public void testNextLongBadBounds() {
256	jsr166	1.19	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	dl	1.1	}
269
270			/**
271			* nextLong(bound) returns 0 <= value < bound;
272	jsr166	1.14	* repeated calls produce at least two distinct results
273	dl	1.1	*/
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	jsr166	1.2	while (i < NCALLS &&
281	dl	1.1	(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	jsr166	1.14	* repeated calls produce at least two distinct results
292	dl	1.1	*/
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	jsr166	1.2	while (i < NCALLS &&
301	dl	1.1	(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	jsr166	1.19	* 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	dl	1.1	* nextDouble(least, bound) returns least <= value < bound;
332	jsr166	1.14	* repeated calls produce at least two distinct results
333	dl	1.1	*/
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	jsr166	1.2	while (i < NCALLS &&
342	dl	1.1	(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	jsr166	1.11	/**
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	jsr166	1.18	Runnable getRandomState = new CheckedRunnable() {
365	jsr166	1.11	public void realRun() {
366			ThreadLocalRandom current = ThreadLocalRandom.current();
367			assertSame(current, ThreadLocalRandom.current());
368	dl	1.12	// test bug: the following is not guaranteed and not true in JDK8
369			// assertNotSame(current, threadLocalRandom.get());
370	jsr166	1.11	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	jsr166	1.26	/**
389			* Repeated calls to nextBytes produce at least values of different signs for every byte
390			*/
391			public void testNextBytes() {
392			ThreadLocalRandom rnd = ThreadLocalRandom.current();
393			int n = rnd.nextInt(20);
394			byte[] bytes = new byte[n];
395			outer:
396			for (int i = 0; i < n; i++) {
397			for (int tries = NCALLS; tries-->0; ) {
398			byte before = bytes[i];
399			rnd.nextBytes(bytes);
400			byte after = bytes[i];
401			if (after * before < 0)
402			continue outer;
403			}
404			fail("not enough variation in random bytes");
405			}
406			}
407
408	dl	1.1	}