android-platform-libcore/luni/src/test/java/tests/api/java/util/concurrent/CountDownLatchTest.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/licenses/publicdomain
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

package tests.api.java.util.concurrent; // android-added

import junit.framework.*;
import java.util.*;
import java.util.concurrent.*;
import static java.util.concurrent.TimeUnit.MILLISECONDS;

public class CountDownLatchTest extends JSR166TestCase {
    public static Test suite() {
        return new TestSuite(CountDownLatchTest.class);
    }

    /**
     * negative constructor argument throws IAE
     */
    public void testConstructor() {
        try {
            new CountDownLatch(-1);
            shouldThrow();
        } catch (IllegalArgumentException success) {}
    }

    /**
     * getCount returns initial count and decreases after countDown
     */
    public void testGetCount() {
        final CountDownLatch l = new CountDownLatch(2);
        assertEquals(2, l.getCount());
        l.countDown();
        assertEquals(1, l.getCount());
    }

    /**
     * countDown decrements count when positive and has no effect when zero
     */
    public void testCountDown() {
        final CountDownLatch l = new CountDownLatch(1);
        assertEquals(1, l.getCount());
        l.countDown();
        assertEquals(0, l.getCount());
        l.countDown();
        assertEquals(0, l.getCount());
    }

    /**
     * await returns after countDown to zero, but not before
     */
    public void testAwait() throws InterruptedException {
        final CountDownLatch l = new CountDownLatch(2);

        Thread t = new Thread(new CheckedRunnable() {
            public void realRun() throws InterruptedException {
                threadAssertTrue(l.getCount() > 0);
                l.await();
                threadAssertTrue(l.getCount() == 0);
            }});

        t.start();
        assertEquals(l.getCount(), 2);
        Thread.sleep(SHORT_DELAY_MS);
        l.countDown();
        assertEquals(l.getCount(), 1);
        l.countDown();
        assertEquals(l.getCount(), 0);
        t.join();
    }


    /**
     * timed await returns after countDown to zero
     */
    public void testTimedAwait() throws InterruptedException {
        final CountDownLatch l = new CountDownLatch(2);

        Thread t = new Thread(new CheckedRunnable() {
            public void realRun() throws InterruptedException {
                threadAssertTrue(l.getCount() > 0);
                threadAssertTrue(l.await(SMALL_DELAY_MS, MILLISECONDS));
            }});

        t.start();
        assertEquals(l.getCount(), 2);
        Thread.sleep(SHORT_DELAY_MS);
        l.countDown();
        assertEquals(l.getCount(), 1);
        l.countDown();
        assertEquals(l.getCount(), 0);
        t.join();
    }

    /**
     * await throws IE if interrupted before counted down
     */
    public void testAwait_InterruptedException() throws InterruptedException {
        final CountDownLatch l = new CountDownLatch(1);
        Thread t = new Thread(new CheckedInterruptedRunnable() {
            public void realRun() throws InterruptedException {
                threadAssertTrue(l.getCount() > 0);
                l.await();
            }});

        t.start();
        assertEquals(l.getCount(), 1);
        t.interrupt();
        t.join();
    }

    /**
     * timed await throws IE if interrupted before counted down
     */
    public void testTimedAwait_InterruptedException() throws InterruptedException {
        final CountDownLatch l = new CountDownLatch(1);
        Thread t = new Thread(new CheckedInterruptedRunnable() {
            public void realRun() throws InterruptedException {
                threadAssertTrue(l.getCount() > 0);
                l.await(MEDIUM_DELAY_MS, MILLISECONDS);
            }});

        t.start();
        Thread.sleep(SHORT_DELAY_MS);
        assertEquals(l.getCount(), 1);
        t.interrupt();
        t.join();
    }

    /**
     * timed await times out if not counted down before timeout
     */
    public void testAwaitTimeout() throws InterruptedException {
        final CountDownLatch l = new CountDownLatch(1);
        Thread t = new Thread(new CheckedRunnable() {
            public void realRun() throws InterruptedException {
                threadAssertTrue(l.getCount() > 0);
                threadAssertFalse(l.await(SHORT_DELAY_MS, MILLISECONDS));
                threadAssertTrue(l.getCount() > 0);
            }});

        t.start();
        assertEquals(l.getCount(), 1);
        t.join();
    }

    /**
     * toString indicates current count
     */
    public void testToString() {
        CountDownLatch s = new CountDownLatch(2);
        String us = s.toString();
        assertTrue(us.indexOf("Count = 2") >= 0);
        s.countDown();
        String s1 = s.toString();
        assertTrue(s1.indexOf("Count = 1") >= 0);
        s.countDown();
        String s2 = s.toString();
        assertTrue(s2.indexOf("Count = 0") >= 0);
    }

}