/*
 * 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/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

import junit.framework.*;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Arrays;
import java.util.NoSuchElementException;
import java.util.PropertyPermission;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicReference;
import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static java.util.concurrent.TimeUnit.NANOSECONDS;
import java.security.CodeSource;
import java.security.Permission;
import java.security.PermissionCollection;
import java.security.Permissions;
import java.security.Policy;
import java.security.ProtectionDomain;
import java.security.SecurityPermission;

/**
 * Base class for JSR166 Junit TCK tests.  Defines some constants,
 * utility methods and classes, as well as a simple framework for
 * helping to make sure that assertions failing in generated threads
 * cause the associated test that generated them to itself fail (which
 * JUnit does not otherwise arrange).  The rules for creating such
 * tests are:
 *
 * <ol>
 *
 * <li> All assertions in code running in generated threads must use
 * the forms {@link #threadFail}, {@link #threadAssertTrue}, {@link
 * #threadAssertEquals}, or {@link #threadAssertNull}, (not
 * {@code fail}, {@code assertTrue}, etc.) It is OK (but not
 * particularly recommended) for other code to use these forms too.
 * Only the most typically used JUnit assertion methods are defined
 * this way, but enough to live with.</li>
 *
 * <li> If you override {@link #setUp} or {@link #tearDown}, make sure
 * to invoke {@code super.setUp} and {@code super.tearDown} within
 * them. These methods are used to clear and check for thread
 * assertion failures.</li>
 *
 * <li>All delays and timeouts must use one of the constants {@code
 * SHORT_DELAY_MS}, {@code SMALL_DELAY_MS}, {@code MEDIUM_DELAY_MS},
 * {@code LONG_DELAY_MS}. The idea here is that a SHORT is always
 * discriminable from zero time, and always allows enough time for the
 * small amounts of computation (creating a thread, calling a few
 * methods, etc) needed to reach a timeout point. Similarly, a SMALL
 * is always discriminable as larger than SHORT and smaller than
 * MEDIUM.  And so on. These constants are set to conservative values,
 * but even so, if there is ever any doubt, they can all be increased
 * in one spot to rerun tests on slower platforms.</li>
 *
 * <li> All threads generated must be joined inside each test case
 * method (or {@code fail} to do so) before returning from the
 * method. The {@code joinPool} method can be used to do this when
 * using Executors.</li>
 *
 * </ol>
 *
 * <p> <b>Other notes</b>
 * <ul>
 *
 * <li> Usually, there is one testcase method per JSR166 method
 * covering "normal" operation, and then as many exception-testing
 * methods as there are exceptions the method can throw. Sometimes
 * there are multiple tests per JSR166 method when the different
 * "normal" behaviors differ significantly. And sometimes testcases
 * cover multiple methods when they cannot be tested in
 * isolation.</li>
 *
 * <li> The documentation style for testcases is to provide as javadoc
 * a simple sentence or two describing the property that the testcase
 * method purports to test. The javadocs do not say anything about how
 * the property is tested. To find out, read the code.</li>
 *
 * <li> These tests are "conformance tests", and do not attempt to
 * test throughput, latency, scalability or other performance factors
 * (see the separate "jtreg" tests for a set intended to check these
 * for the most central aspects of functionality.) So, most tests use
 * the smallest sensible numbers of threads, collection sizes, etc
 * needed to check basic conformance.</li>
 *
 * <li>The test classes currently do not declare inclusion in
 * any particular package to simplify things for people integrating
 * them in TCK test suites.</li>
 *
 * <li> As a convenience, the {@code main} of this class (JSR166TestCase)
 * runs all JSR166 unit tests.</li>
 *
 * </ul>
 */
public class JSR166TestCase extends TestCase {
    private static final boolean useSecurityManager =
        Boolean.getBoolean("jsr166.useSecurityManager");

    protected static final boolean expensiveTests =
        Boolean.getBoolean("jsr166.expensiveTests");

    /**
     * If true, report on stdout all "slow" tests, that is, ones that
     * take more than profileThreshold milliseconds to execute.
     */
    private static final boolean profileTests =
        Boolean.getBoolean("jsr166.profileTests");

    /**
     * The number of milliseconds that tests are permitted for
     * execution without being reported, when profileTests is set.
     */
    private static final long profileThreshold =
        Long.getLong("jsr166.profileThreshold", 100);

    protected void runTest() throws Throwable {
        if (profileTests)
            runTestProfiled();
        else
            super.runTest();
    }

    protected void runTestProfiled() throws Throwable {
        long t0 = System.nanoTime();
        try {
            super.runTest();
        } finally {
            long elapsedMillis =
                (System.nanoTime() - t0) / (1000L * 1000L);
            if (elapsedMillis >= profileThreshold)
                System.out.printf("%n%s: %d%n", toString(), elapsedMillis);
        }
    }

    /**
     * Runs all JSR166 unit tests using junit.textui.TestRunner
     */
    public static void main(String[] args) {
        if (useSecurityManager) {
            System.err.println("Setting a permissive security manager");
            Policy.setPolicy(permissivePolicy());
            System.setSecurityManager(new SecurityManager());
        }
        int iters = (args.length == 0) ? 1 : Integer.parseInt(args[0]);

        Test s = suite();
        for (int i = 0; i < iters; ++i) {
            junit.textui.TestRunner.run(s);
            System.gc();
            System.runFinalization();
        }
        System.exit(0);
    }

    public static TestSuite newTestSuite(Object... suiteOrClasses) {
        TestSuite suite = new TestSuite();
        for (Object suiteOrClass : suiteOrClasses) {
            if (suiteOrClass instanceof TestSuite)
                suite.addTest((TestSuite) suiteOrClass);
            else if (suiteOrClass instanceof Class)
                suite.addTest(new TestSuite((Class<?>) suiteOrClass));
            else
                throw new ClassCastException("not a test suite or class");
        }
        return suite;
    }

    /**
     * Collects all JSR166 unit tests as one suite.
     */
    public static Test suite() {
        return newTestSuite(
            ForkJoinPoolTest.suite(),
            ForkJoinTaskTest.suite(),
            RecursiveActionTest.suite(),
            RecursiveTaskTest.suite(),
            LinkedTransferQueueTest.suite(),
            PhaserTest.suite(),
            ThreadLocalRandomTest.suite(),
            AbstractExecutorServiceTest.suite(),
            AbstractQueueTest.suite(),
            AbstractQueuedSynchronizerTest.suite(),
            AbstractQueuedLongSynchronizerTest.suite(),
            ArrayBlockingQueueTest.suite(),
            ArrayDequeTest.suite(),
            AtomicBooleanTest.suite(),
            AtomicIntegerArrayTest.suite(),
            AtomicIntegerFieldUpdaterTest.suite(),
            AtomicIntegerTest.suite(),
            AtomicLongArrayTest.suite(),
            AtomicLongFieldUpdaterTest.suite(),
            AtomicLongTest.suite(),
            AtomicMarkableReferenceTest.suite(),
            AtomicReferenceArrayTest.suite(),
            AtomicReferenceFieldUpdaterTest.suite(),
            AtomicReferenceTest.suite(),
            AtomicStampedReferenceTest.suite(),
            ConcurrentHashMapTest.suite(),
            ConcurrentLinkedDequeTest.suite(),
            ConcurrentLinkedQueueTest.suite(),
            ConcurrentSkipListMapTest.suite(),
            ConcurrentSkipListSubMapTest.suite(),
            ConcurrentSkipListSetTest.suite(),
            ConcurrentSkipListSubSetTest.suite(),
            CopyOnWriteArrayListTest.suite(),
            CopyOnWriteArraySetTest.suite(),
            CountDownLatchTest.suite(),
            CyclicBarrierTest.suite(),
            DelayQueueTest.suite(),
            EntryTest.suite(),
            ExchangerTest.suite(),
            ExecutorsTest.suite(),
            ExecutorCompletionServiceTest.suite(),
            FutureTaskTest.suite(),
            LinkedBlockingDequeTest.suite(),
            LinkedBlockingQueueTest.suite(),
            LinkedListTest.suite(),
            LockSupportTest.suite(),
            PriorityBlockingQueueTest.suite(),
            PriorityQueueTest.suite(),
            ReentrantLockTest.suite(),
            ReentrantReadWriteLockTest.suite(),
            ScheduledExecutorTest.suite(),
            ScheduledExecutorSubclassTest.suite(),
            SemaphoreTest.suite(),
            SynchronousQueueTest.suite(),
            SystemTest.suite(),
            ThreadLocalTest.suite(),
            ThreadPoolExecutorTest.suite(),
            ThreadPoolExecutorSubclassTest.suite(),
            ThreadTest.suite(),
            TimeUnitTest.suite(),
            TreeMapTest.suite(),
            TreeSetTest.suite(),
            TreeSubMapTest.suite(),
            TreeSubSetTest.suite());
    }


    public static long SHORT_DELAY_MS;
    public static long SMALL_DELAY_MS;
    public static long MEDIUM_DELAY_MS;
    public static long LONG_DELAY_MS;


    /**
     * Returns the shortest timed delay. This could
     * be reimplemented to use for example a Property.
     */
    protected long getShortDelay() {
        return 50;
    }


    /**
     * Sets delays as multiples of SHORT_DELAY.
     */
    protected void setDelays() {
        SHORT_DELAY_MS = getShortDelay();
        SMALL_DELAY_MS  = SHORT_DELAY_MS * 5;
        MEDIUM_DELAY_MS = SHORT_DELAY_MS * 10;
        LONG_DELAY_MS   = SHORT_DELAY_MS * 200;
    }

    /**
     * The first exception encountered if any threadAssertXXX method fails.
     */
    private final AtomicReference<Throwable> threadFailure
        = new AtomicReference<Throwable>(null);

    /**
     * Records an exception so that it can be rethrown later in the test
     * harness thread, triggering a test case failure.  Only the first
     * failure is recorded; subsequent calls to this method from within
     * the same test have no effect.
     */
    public void threadRecordFailure(Throwable t) {
        threadFailure.compareAndSet(null, t);
    }

    public void setUp() {
        setDelays();
    }

    /**
     * Triggers test case failure if any thread assertions have failed,
     * by rethrowing, in the test harness thread, any exception recorded
     * earlier by threadRecordFailure.
     */
    public void tearDown() throws Exception {
        Throwable t = threadFailure.getAndSet(null);
        if (t != null) {
            if (t instanceof Error)
                throw (Error) t;
            else if (t instanceof RuntimeException)
                throw (RuntimeException) t;
            else if (t instanceof Exception)
                throw (Exception) t;
            else {
                AssertionFailedError afe =
                    new AssertionFailedError(t.toString());
                afe.initCause(t);
                throw afe;
            }
        }
    }

    /**
     * Just like fail(reason), but additionally recording (using
     * threadRecordFailure) any AssertionFailedError thrown, so that
     * the current testcase will fail.
     */
    public void threadFail(String reason) {
        try {
            fail(reason);
        } catch (AssertionFailedError t) {
            threadRecordFailure(t);
            fail(reason);
        }
    }

    /**
     * Just like assertTrue(b), but additionally recording (using
     * threadRecordFailure) any AssertionFailedError thrown, so that
     * the current testcase will fail.
     */
    public void threadAssertTrue(boolean b) {
        try {
            assertTrue(b);
        } catch (AssertionFailedError t) {
            threadRecordFailure(t);
            throw t;
        }
    }

    /**
     * Just like assertFalse(b), but additionally recording (using
     * threadRecordFailure) any AssertionFailedError thrown, so that
     * the current testcase will fail.
     */
    public void threadAssertFalse(boolean b) {
        try {
            assertFalse(b);
        } catch (AssertionFailedError t) {
            threadRecordFailure(t);
            throw t;
        }
    }

    /**
     * Just like assertNull(x), but additionally recording (using
     * threadRecordFailure) any AssertionFailedError thrown, so that
     * the current testcase will fail.
     */
    public void threadAssertNull(Object x) {
        try {
            assertNull(x);
        } catch (AssertionFailedError t) {
            threadRecordFailure(t);
            throw t;
        }
    }

    /**
     * Just like assertEquals(x, y), but additionally recording (using
     * threadRecordFailure) any AssertionFailedError thrown, so that
     * the current testcase will fail.
     */
    public void threadAssertEquals(long x, long y) {
        try {
            assertEquals(x, y);
        } catch (AssertionFailedError t) {
            threadRecordFailure(t);
            throw t;
        }
    }

    /**
     * Just like assertEquals(x, y), but additionally recording (using
     * threadRecordFailure) any AssertionFailedError thrown, so that
     * the current testcase will fail.
     */
    public void threadAssertEquals(Object x, Object y) {
        try {
            assertEquals(x, y);
        } catch (AssertionFailedError t) {
            threadRecordFailure(t);
            throw t;
        } catch (Throwable t) {
            threadUnexpectedException(t);
        }
    }

    /**
     * Just like assertSame(x, y), but additionally recording (using
     * threadRecordFailure) any AssertionFailedError thrown, so that
     * the current testcase will fail.
     */
    public void threadAssertSame(Object x, Object y) {
        try {
            assertSame(x, y);
        } catch (AssertionFailedError t) {
            threadRecordFailure(t);
            throw t;
        }
    }

    /**
     * Calls threadFail with message "should throw exception".
     */
    public void threadShouldThrow() {
        threadFail("should throw exception");
    }

    /**
     * Calls threadFail with message "should throw" + exceptionName.
     */
    public void threadShouldThrow(String exceptionName) {
        threadFail("should throw " + exceptionName);
    }

    /**
     * Records the given exception using {@link #threadRecordFailure},
     * then rethrows the exception, wrapping it in an
     * AssertionFailedError if necessary.
     */
    public void threadUnexpectedException(Throwable t) {
        threadRecordFailure(t);
        t.printStackTrace();
        if (t instanceof RuntimeException)
            throw (RuntimeException) t;
        else if (t instanceof Error)
            throw (Error) t;
        else {
            AssertionFailedError afe =
                new AssertionFailedError("unexpected exception: " + t);
            t.initCause(t);
            throw afe;
        }
    }

    /**
     * Delays, via Thread.sleep for the given millisecond delay, but
     * if the sleep is shorter than specified, may re-sleep or yield
     * until time elapses.
     */
    public static void delay(long millis) throws InterruptedException {
        long startTime = System.nanoTime();
        long ns = millis * 1000 * 1000;
        for (;;) {
            if (millis > 0L)
                Thread.sleep(millis);
            else // too short to sleep
                Thread.yield();
            long d = ns - (System.nanoTime() - startTime);
            if (d > 0L)
                millis = d / (1000 * 1000);
            else
                break;
        }
    }

    /**
     * Waits out termination of a thread pool or fails doing so.
     */
    public void joinPool(ExecutorService exec) {
        try {
            exec.shutdown();
            assertTrue("ExecutorService did not terminate in a timely manner",
                       exec.awaitTermination(2 * LONG_DELAY_MS, MILLISECONDS));
        } catch (SecurityException ok) {
            // Allowed in case test doesn't have privs
        } catch (InterruptedException ie) {
            fail("Unexpected InterruptedException");
        }
    }

    /**
     * Checks that thread does not terminate within the given millisecond delay.
     */
    public void assertThreadStaysAlive(Thread thread, long millis) {
        try {
            // No need to optimize the failing case via Thread.join.
            delay(millis);
            assertTrue(thread.isAlive());
        } catch (InterruptedException ie) {
            fail("Unexpected InterruptedException");
        }
    }

    /**
     * Fails with message "should throw exception".
     */
    public void shouldThrow() {
        fail("Should throw exception");
    }

    /**
     * Fails with message "should throw " + exceptionName.
     */
    public void shouldThrow(String exceptionName) {
        fail("Should throw " + exceptionName);
    }

    /**
     * The number of elements to place in collections, arrays, etc.
     */
    public static final int SIZE = 20;

    // Some convenient Integer constants

    public static final Integer zero  = new Integer(0);
    public static final Integer one   = new Integer(1);
    public static final Integer two   = new Integer(2);
    public static final Integer three = new Integer(3);
    public static final Integer four  = new Integer(4);
    public static final Integer five  = new Integer(5);
    public static final Integer six   = new Integer(6);
    public static final Integer seven = new Integer(7);
    public static final Integer eight = new Integer(8);
    public static final Integer nine  = new Integer(9);
    public static final Integer m1  = new Integer(-1);
    public static final Integer m2  = new Integer(-2);
    public static final Integer m3  = new Integer(-3);
    public static final Integer m4  = new Integer(-4);
    public static final Integer m5  = new Integer(-5);
    public static final Integer m6  = new Integer(-6);
    public static final Integer m10 = new Integer(-10);


    /**
     * Runs Runnable r with a security policy that permits precisely
     * the specified permissions.  If there is no current security
     * manager, the runnable is run twice, both with and without a
     * security manager.  We require that any security manager permit
     * getPolicy/setPolicy.
     */
    public void runWithPermissions(Runnable r, Permission... permissions) {
        SecurityManager sm = System.getSecurityManager();
        if (sm == null) {
            r.run();
            Policy savedPolicy = Policy.getPolicy();
            try {
                Policy.setPolicy(permissivePolicy());
                System.setSecurityManager(new SecurityManager());
                runWithPermissions(r, permissions);
            } finally {
                System.setSecurityManager(null);
                Policy.setPolicy(savedPolicy);
            }
        } else {
            Policy savedPolicy = Policy.getPolicy();
            AdjustablePolicy policy = new AdjustablePolicy(permissions);
            Policy.setPolicy(policy);

            try {
                r.run();
            } finally {
                policy.addPermission(new SecurityPermission("setPolicy"));
                Policy.setPolicy(savedPolicy);
            }
        }
    }

    /**
     * Runs a runnable without any permissions.
     */
    public void runWithoutPermissions(Runnable r) {
        runWithPermissions(r);
    }

    /**
     * A security policy where new permissions can be dynamically added
     * or all cleared.
     */
    public static class AdjustablePolicy extends java.security.Policy {
        Permissions perms = new Permissions();
        AdjustablePolicy(Permission... permissions) {
            for (Permission permission : permissions)
                perms.add(permission);
        }
        void addPermission(Permission perm) { perms.add(perm); }
        void clearPermissions() { perms = new Permissions(); }
        public PermissionCollection getPermissions(CodeSource cs) {
            return perms;
        }
        public PermissionCollection getPermissions(ProtectionDomain pd) {
            return perms;
        }
        public boolean implies(ProtectionDomain pd, Permission p) {
            return perms.implies(p);
        }
        public void refresh() {}
    }

    /**
     * Returns a policy containing all the permissions we ever need.
     */
    public static Policy permissivePolicy() {
        return new AdjustablePolicy
            // Permissions j.u.c. needs directly
            (new RuntimePermission("modifyThread"),
             new RuntimePermission("getClassLoader"),
             new RuntimePermission("setContextClassLoader"),
             // Permissions needed to change permissions!
             new SecurityPermission("getPolicy"),
             new SecurityPermission("setPolicy"),
             new RuntimePermission("setSecurityManager"),
             // Permissions needed by the junit test harness
             new RuntimePermission("accessDeclaredMembers"),
             new PropertyPermission("*", "read"),
             new java.io.FilePermission("<<ALL FILES>>", "read"));
    }

    /**
     * Sleeps until the given time has elapsed.
     * Throws AssertionFailedError if interrupted.
     */
    void sleep(long millis) {
        try {
            delay(millis);
        } catch (InterruptedException ie) {
            AssertionFailedError afe =
                new AssertionFailedError("Unexpected InterruptedException");
            afe.initCause(ie);
            throw afe;
        }
    }

    /**
     * Sleeps until the timeout has elapsed, or interrupted.
     * Does <em>NOT</em> throw InterruptedException.
     */
    void sleepTillInterrupted(long timeoutMillis) {
        try {
            Thread.sleep(timeoutMillis);
        } catch (InterruptedException wakeup) {}
    }

    /**
     * Waits up to the specified number of milliseconds for the given
     * thread to enter a wait state: BLOCKED, WAITING, or TIMED_WAITING.
     */
    void waitForThreadToEnterWaitState(Thread thread, long timeoutMillis) {
        long timeoutNanos = timeoutMillis * 1000L * 1000L;
        long t0 = System.nanoTime();
        for (;;) {
            Thread.State s = thread.getState();
            if (s == Thread.State.BLOCKED ||
                s == Thread.State.WAITING ||
                s == Thread.State.TIMED_WAITING)
                return;
            else if (s == Thread.State.TERMINATED)
                fail("Unexpected thread termination");
            else if (System.nanoTime() - t0 > timeoutNanos) {
                threadAssertTrue(thread.isAlive());
                return;
            }
            Thread.yield();
        }
    }

    /**
     * Waits up to LONG_DELAY_MS for the given thread to enter a wait
     * state: BLOCKED, WAITING, or TIMED_WAITING.
     */
    void waitForThreadToEnterWaitState(Thread thread) {
        waitForThreadToEnterWaitState(thread, LONG_DELAY_MS);
    }

    /**
     * Returns the number of milliseconds since time given by
     * startNanoTime, which must have been previously returned from a
     * call to {@link System.nanoTime()}.
     */
    long millisElapsedSince(long startNanoTime) {
        return NANOSECONDS.toMillis(System.nanoTime() - startNanoTime);
    }

    /**
     * Returns a new started daemon Thread running the given runnable.
     */
    Thread newStartedThread(Runnable runnable) {
        Thread t = new Thread(runnable);
        t.setDaemon(true);
        t.start();
        return t;
    }

    /**
     * Waits for the specified time (in milliseconds) for the thread
     * to terminate (using {@link Thread#join(long)}), else interrupts
     * the thread (in the hope that it may terminate later) and fails.
     */
    void awaitTermination(Thread t, long timeoutMillis) {
        try {
            t.join(timeoutMillis);
        } catch (InterruptedException ie) {
            threadUnexpectedException(ie);
        } finally {
            if (t.isAlive()) {
                t.interrupt();
                fail("Test timed out");
            }
        }
    }

    /**
     * Waits for LONG_DELAY_MS milliseconds for the thread to
     * terminate (using {@link Thread#join(long)}), else interrupts
     * the thread (in the hope that it may terminate later) and fails.
     */
    void awaitTermination(Thread t) {
        awaitTermination(t, LONG_DELAY_MS);
    }

    // Some convenient Runnable classes

    public abstract class CheckedRunnable implements Runnable {
        protected abstract void realRun() throws Throwable;

        public final void run() {
            try {
                realRun();
            } catch (Throwable t) {
                threadUnexpectedException(t);
            }
        }
    }

    public abstract class RunnableShouldThrow implements Runnable {
        protected abstract void realRun() throws Throwable;

        final Class<?> exceptionClass;

        <T extends Throwable> RunnableShouldThrow(Class<T> exceptionClass) {
            this.exceptionClass = exceptionClass;
        }

        public final void run() {
            try {
                realRun();
                threadShouldThrow(exceptionClass.getSimpleName());
            } catch (Throwable t) {
                if (! exceptionClass.isInstance(t))
                    threadUnexpectedException(t);
            }
        }
    }

    public abstract class ThreadShouldThrow extends Thread {
        protected abstract void realRun() throws Throwable;

        final Class<?> exceptionClass;

        <T extends Throwable> ThreadShouldThrow(Class<T> exceptionClass) {
            this.exceptionClass = exceptionClass;
        }

        public final void run() {
            try {
                realRun();
                threadShouldThrow(exceptionClass.getSimpleName());
            } catch (Throwable t) {
                if (! exceptionClass.isInstance(t))
                    threadUnexpectedException(t);
            }
        }
    }

    public abstract class CheckedInterruptedRunnable implements Runnable {
        protected abstract void realRun() throws Throwable;

        public final void run() {
            try {
                realRun();
                threadShouldThrow("InterruptedException");
            } catch (InterruptedException success) {
            } catch (Throwable t) {
                threadUnexpectedException(t);
            }
        }
    }

    public abstract class CheckedCallable<T> implements Callable<T> {
        protected abstract T realCall() throws Throwable;

        public final T call() {
            try {
                return realCall();
            } catch (Throwable t) {
                threadUnexpectedException(t);
                return null;
            }
        }
    }

    public abstract class CheckedInterruptedCallable<T>
        implements Callable<T> {
        protected abstract T realCall() throws Throwable;

        public final T call() {
            try {
                T result = realCall();
                threadShouldThrow("InterruptedException");
                return result;
            } catch (InterruptedException success) {
            } catch (Throwable t) {
                threadUnexpectedException(t);
            }
            return null;
        }
    }

    public static class NoOpRunnable implements Runnable {
        public void run() {}
    }

    public static class NoOpCallable implements Callable {
        public Object call() { return Boolean.TRUE; }
    }

    public static final String TEST_STRING = "a test string";

    public static class StringTask implements Callable<String> {
        public String call() { return TEST_STRING; }
    }

    public Callable<String> latchAwaitingStringTask(final CountDownLatch latch) {
        return new CheckedCallable<String>() {
            protected String realCall() {
                try {
                    latch.await();
                } catch (InterruptedException quittingTime) {}
                return TEST_STRING;
            }};
    }

    public Runnable awaiter(final CountDownLatch latch) {
        return new CheckedRunnable() {
            public void realRun() throws InterruptedException {
                await(latch);
            }};
    }

    public void await(CountDownLatch latch) {
        try {
            assertTrue(latch.await(LONG_DELAY_MS, MILLISECONDS));
        } catch (Throwable t) {
            threadUnexpectedException(t);
        }
    }

    public static class NPETask implements Callable<String> {
        public String call() { throw new NullPointerException(); }
    }

    public static class CallableOne implements Callable<Integer> {
        public Integer call() { return one; }
    }

    public class ShortRunnable extends CheckedRunnable {
        protected void realRun() throws Throwable {
            delay(SHORT_DELAY_MS);
        }
    }

    public class ShortInterruptedRunnable extends CheckedInterruptedRunnable {
        protected void realRun() throws InterruptedException {
            delay(SHORT_DELAY_MS);
        }
    }

    public class SmallRunnable extends CheckedRunnable {
        protected void realRun() throws Throwable {
            delay(SMALL_DELAY_MS);
        }
    }

    public class SmallPossiblyInterruptedRunnable extends CheckedRunnable {
        protected void realRun() {
            try {
                delay(SMALL_DELAY_MS);
            } catch (InterruptedException ok) {}
        }
    }

    public class SmallCallable extends CheckedCallable {
        protected Object realCall() throws InterruptedException {
            delay(SMALL_DELAY_MS);
            return Boolean.TRUE;
        }
    }

    public class MediumRunnable extends CheckedRunnable {
        protected void realRun() throws Throwable {
            delay(MEDIUM_DELAY_MS);
        }
    }

    public class MediumInterruptedRunnable extends CheckedInterruptedRunnable {
        protected void realRun() throws InterruptedException {
            delay(MEDIUM_DELAY_MS);
        }
    }

    public Runnable possiblyInterruptedRunnable(final long timeoutMillis) {
        return new CheckedRunnable() {
            protected void realRun() {
                try {
                    delay(timeoutMillis);
                } catch (InterruptedException ok) {}
            }};
    }

    public class MediumPossiblyInterruptedRunnable extends CheckedRunnable {
        protected void realRun() {
            try {
                delay(MEDIUM_DELAY_MS);
            } catch (InterruptedException ok) {}
        }
    }

    public class LongPossiblyInterruptedRunnable extends CheckedRunnable {
        protected void realRun() {
            try {
                delay(LONG_DELAY_MS);
            } catch (InterruptedException ok) {}
        }
    }

    /**
     * For use as ThreadFactory in constructors
     */
    public static class SimpleThreadFactory implements ThreadFactory {
        public Thread newThread(Runnable r) {
            return new Thread(r);
        }
    }

    public interface TrackedRunnable extends Runnable {
        boolean isDone();
    }

    public static TrackedRunnable trackedRunnable(final long timeoutMillis) {
        return new TrackedRunnable() {
                private volatile boolean done = false;
                public boolean isDone() { return done; }
                public void run() {
                    try {
                        delay(timeoutMillis);
                        done = true;
                    } catch (InterruptedException ok) {}
                }
            };
    }

    public static class TrackedShortRunnable implements Runnable {
        public volatile boolean done = false;
        public void run() {
            try {
                delay(SHORT_DELAY_MS);
                done = true;
            } catch (InterruptedException ok) {}
        }
    }

    public static class TrackedSmallRunnable implements Runnable {
        public volatile boolean done = false;
        public void run() {
            try {
                delay(SMALL_DELAY_MS);
                done = true;
            } catch (InterruptedException ok) {}
        }
    }

    public static class TrackedMediumRunnable implements Runnable {
        public volatile boolean done = false;
        public void run() {
            try {
                delay(MEDIUM_DELAY_MS);
                done = true;
            } catch (InterruptedException ok) {}
        }
    }

    public static class TrackedLongRunnable implements Runnable {
        public volatile boolean done = false;
        public void run() {
            try {
                delay(LONG_DELAY_MS);
                done = true;
            } catch (InterruptedException ok) {}
        }
    }

    public static class TrackedNoOpRunnable implements Runnable {
        public volatile boolean done = false;
        public void run() {
            done = true;
        }
    }

    public static class TrackedCallable implements Callable {
        public volatile boolean done = false;
        public Object call() {
            try {
                delay(SMALL_DELAY_MS);
                done = true;
            } catch (InterruptedException ok) {}
            return Boolean.TRUE;
        }
    }

    /**
     * Analog of CheckedRunnable for RecursiveAction
     */
    public abstract class CheckedRecursiveAction extends RecursiveAction {
        protected abstract void realCompute() throws Throwable;

        public final void compute() {
            try {
                realCompute();
            } catch (Throwable t) {
                threadUnexpectedException(t);
            }
        }
    }

    /**
     * Analog of CheckedCallable for RecursiveTask
     */
    public abstract class CheckedRecursiveTask<T> extends RecursiveTask<T> {
        protected abstract T realCompute() throws Throwable;

        public final T compute() {
            try {
                return realCompute();
            } catch (Throwable t) {
                threadUnexpectedException(t);
                return null;
            }
        }
    }

    /**
     * For use as RejectedExecutionHandler in constructors
     */
    public static class NoOpREHandler implements RejectedExecutionHandler {
        public void rejectedExecution(Runnable r,
                                      ThreadPoolExecutor executor) {}
    }

    /**
     * A CyclicBarrier that fails with AssertionFailedErrors instead
     * of throwing checked exceptions.
     */
    public class CheckedBarrier extends CyclicBarrier {
        public CheckedBarrier(int parties) { super(parties); }

        public int await() {
            try {
                return super.await();
            } catch (Exception e) {
                AssertionFailedError afe =
                    new AssertionFailedError("Unexpected exception: " + e);
                afe.initCause(e);
                throw afe;
            }
        }
    }

    public void checkEmpty(BlockingQueue q) {
        try {
            assertTrue(q.isEmpty());
            assertEquals(0, q.size());
            assertNull(q.peek());
            assertNull(q.poll());
            assertNull(q.poll(0, MILLISECONDS));
            assertEquals(q.toString(), "[]");
            assertTrue(Arrays.equals(q.toArray(), new Object[0]));
            assertFalse(q.iterator().hasNext());
            try {
                q.element();
                shouldThrow();
            } catch (NoSuchElementException success) {}
            try {
                q.iterator().next();
                shouldThrow();
            } catch (NoSuchElementException success) {}
            try {
                q.remove();
                shouldThrow();
            } catch (NoSuchElementException success) {}
        } catch (InterruptedException ie) {
            threadUnexpectedException(ie);
        }
    }

    @SuppressWarnings("unchecked")
    public <T> T serialClone(T o) {
        try {
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(bos);
            oos.writeObject(o);
            oos.flush();
            oos.close();
            ByteArrayInputStream bin =
                new ByteArrayInputStream(bos.toByteArray());
            ObjectInputStream ois = new ObjectInputStream(bin);
            return (T) ois.readObject();
        } catch (Throwable t) {
            threadUnexpectedException(t);
            return null;
        }
    }
}