void testConcurrentAccess() throws InterruptedException {
        // Test thread safety of getInstance
        LogStream.setInstance(testStream);

        final LogStream[] instances = new LogStream[10];
        Thread[] threads = new Thread[10];

        for (int i = 0; i < threads.length; i++) {
            final int index = i;
            threads[i] = new Thread(() -> {
                instances[index] = LogStream.getInstance();

    }

    @Test
    public void testThreadSafety() throws InterruptedException {
        // Test concurrent updates from multiple threads
        Thread[] threads = new Thread[10];

        for (int i = 0; i < threads.length; i++) {
            final int index = i;
            threads[i] = new Thread(() -> {
                for (int j = 0; j < 100; j++) {
                    String name = "file" + index + "_" + j + ".txt";

  }

  /**
   * Add a shutdown hook to wait for thread completion in the given {@link ExecutorService service}.
   * This is useful if the given service uses daemon threads, and we want to keep the JVM from
   * exiting immediately on shutdown, instead giving these daemon threads a chance to terminate
   * normally.
   *
   * @param service ExecutorService which uses daemon threads

            });
        }

        // Start all threads simultaneously
        for (Thread thread : threads) {
            thread.start();
        }

        // Wait for all threads to complete
        for (Thread thread : threads) {
            thread.join();
        }

        // All threads should see the initialized state
        for (boolean result : initResults) {

     *
     * @return the {@link CrawlerContext} for the current thread, or {@code null} if no context is set.
     */
    public static CrawlerContext getCrawlerContext() {
        return CRAWLER_CONTEXT_THREAD_LOCAL.get();
    }

    /**
     * Sets the current {@link CrawlerContext} for the current thread.
     * If the provided {@code crawlerContext} is {@code null}, the context is removed from the thread-local storage.

   * intentionally, so there is no other way to clean up these threads. (The better solution,
   * though, would be to run the tests that use TestThread in separate VMs so that their threads
   * don't hang around during other tests.)
   */
  @Override
  public void tearDown() throws Exception {
    try {
      Thread.class.getMethod("stop").invoke(this);
      join();

   * intentionally, so there is no other way to clean up these threads. (The better solution,
   * though, would be to run the tests that use TestThread in separate VMs so that their threads
   * don't hang around during other tests.)
   */
  @Override
  public void tearDown() throws Exception {
    try {
      Thread.class.getMethod("stop").invoke(this);
      join();

volatile CrawlerStatus status   // DONE, RUNNING
AtomicLong accessCount          // Thread-safe counter
int numOfThread = 10            // Crawler threads
int maxDepth = -1               // Max depth (-1 = unlimited)
long maxAccessCount = 0         // Max URLs (0 = unlimited)
```

### CrawlerThread (`CrawlerThread.java`)

Worker thread for crawling.

/**
 * Simple {@link ThreadFactory} implementation that ensures the corresponding threads have a meaningful name.
 */
public class BuildThreadFactory implements ThreadFactory {
    private final AtomicInteger id = new AtomicInteger();

    private static final String PREFIX = "BuilderThread";

    @Override
    public Thread newThread(Runnable r) {
        return new Thread(r, String.format("%s-%d", PREFIX, id.getAndIncrement()));
    }

            }

            // When
            for (Thread thread : threads) {
                thread.start();
            }
            for (Thread thread : threads) {
                thread.join();
            }

            // Then
            for (int i = 0; i < threadCount; i++) {
                assertTrue(success[i], "Thread " + i + " failed");
            }
        }

        @Test