LockingThread thread = new LockingThread(lockA);
    thread.start();

    thread.waitUntilHoldingLock();
    assertFalse(lockA.tryLock());

    thread.releaseLockAndFinish();
    assertTrue(lockA.tryLock());
  }

  public void testReentrantWriteLock_tryLock() throws Exception {
    LockingThread thread = new LockingThread(writeLockA);
    thread.start();

    LockingThread thread = new LockingThread(lockA);
    thread.start();

    thread.waitUntilHoldingLock();
    assertFalse(lockA.tryLock());

    thread.releaseLockAndFinish();
    assertTrue(lockA.tryLock());
  }

  public void testReentrantWriteLock_tryLock() throws Exception {
    LockingThread thread = new LockingThread(writeLockA);
    thread.start();

        return instance;
    }

    /**
     * 処理を開始します。
     */
    public synchronized void start() {
        if (thread == null) {
            thread = new Thread(this, "CoreLib-TimeoutManager");
            thread.setDaemon(true);
            thread.start();
            if (logger.isDebugEnabled()) {
                logger.debug("TimeoutManager started.");
            }
        }
    }

        final Thread[] threads = new Thread[crawlerContext.getNumOfThread()];
        for (int i = 0; i < crawlerContext.getNumOfThread(); i++) {
            final CrawlerThread crawlerThread = crawlerContainer.getComponent("crawlerThread");
            crawlerThread.setCrawlerContext(crawlerContext);
            crawlerThread.setClientFactory(clientFactory);
            threads[i] =

  }

  /** Receive frames until there are no more. Invoked only by the reader thread. */
  @Throws(IOException::class)
  fun loopReader(response: Response) {
    try {
      listener.onOpen(this@RealWebSocket, response)
      while (receivedCloseCode == -1) {
        // This method call results in one or more onRead* methods being called on this thread.
        reader!!.processNextFrame()
      }
    } catch (e: Exception) {

    }

    @Override
    public int size() {
      assertTrue(Thread.holdsLock(mutex));
      return super.size();
    }

    @Override
    public boolean isEmpty() {
      assertTrue(Thread.holdsLock(mutex));
      return super.isEmpty();
    }

    @Override
    public @Nullable V remove(Object object) {
      assertTrue(Thread.holdsLock(mutex));
      return super.remove(object);
    }

    @Override

import org.codelibs.core.log.Logger;

/**
 * Utility class for Thread class
 *
 * @author shinsuke
 *
 */
public abstract class ThreadUtil {

    private static final Logger logger = Logger.getLogger(ThreadUtil.class);

    public static void sleep(final long millis) {
        if (millis < 1L) {
            return;
        }
        try {
            Thread.sleep(millis);
        } catch (final InterruptedException e) {

     *       observing a null thread does not mean the object is safe to reuse.
     *   <li>If this field's value is some other thread object, we know that it's not our thread.
     *   <li>If this field's value == null because it originally belonged to another thread and that
     *       thread cleared it, we still know that it's not associated with our thread

    assertFalse(future.isDone());
    assertFalse(future.isCancelled());

    CountDownLatch successLatch = new CountDownLatch(1);

    // Run cancellation in a separate thread as an extra thread-safety test.
    new Thread(
            () -> {
              assertThrows(CancellationException.class, future::get);
              successLatch.countDown();
            })
        .start();

        server.start();

        final String url = "http://localhost:7070/";
        try {
            final ResponseData responseData = httpClient.doHead(url);
            Thread.sleep(100);
            assertNotNull(responseData.getLastModified());
            assertTrue(responseData.getLastModified().getTime() < new Date().getTime());
        } finally {
            server.stop();
        }