public static final String HC4_CLIENT = "hc4";

    /** Value for HC5 client selection. */
    public static final String HC5_CLIENT = "hc5";

    /** The HC4 HTTP client instance. */
    protected CrawlerClient hc4Client;

    /** The HC5 HTTP client instance. */
    protected CrawlerClient hc5Client;

    /** Flag indicating which client is selected (true = hc5, false = hc4). */
    private boolean useHc5 = true;

    /**

        }
        return instances;
    }

    /**
     * Checks whether the specified instance is currently active.
     *
     * @param targetInstanceId the instance ID to check.
     * @return {@code true} if the instance is active.
     */
    public boolean isInstanceActive(final String targetInstanceId) {

            throw new CrawlerSystemException("CrawlerClient instance is null. Cannot register null client.");
        }
        clientMap.put(Pattern.compile(regex), client);
    }

    /**
     * Adds a client with a regular expression pattern at a specific position.
     * @param regex The regular expression to match URLs.
     * @param client The CrawlerClient instance.
     * @param pos The position to add the client.
     */

    @Test
    public void test_constructor() {
        assertNotNull(target, "Constructor should create instance");
        assertTrue(target instanceof SystemMonitorTarget, "Instance should be of correct type");
        assertTrue(target instanceof MonitorTarget, "Instance should be a MonitorTarget");
        assertTrue(target instanceof TimeoutTarget, "Instance should be a TimeoutTarget");
    }

    @Test

  private Atomics() {}

  /**
   * Creates an {@code AtomicReference} instance with no initial value.
   *
   * @return a new {@code AtomicReference} with no initial value
   */
  public static <V> AtomicReference<@Nullable V> newReference() {
    return new AtomicReference<>();
  }

  /**
   * Creates an {@code AtomicReference} instance with the given initial value.
   *
   * @param initialValue the initial value

    public static synchronized final SingletonContext getInstance() {
        if (INSTANCE == null) {
            try {
                log.debug("Initializing singleton context");
                init(null);
            } catch (final CIFSException e) {
                log.error("Failed to create singleton JCIFS context", e);
            }
        }
        return INSTANCE;
    }

    /**

  public void testToString() {
    assertThat(INSTANCE.toString()).isEqualTo("{}");
  }

  public void testSize() {
    assertEquals(0, INSTANCE.size());
  }

  public void testGet() {
    assertThat(INSTANCE.get('a', 1)).isNull();
  }

  public void testIsEmpty() {
    assertTrue(INSTANCE.isEmpty());
  }

  public void testCellSet() {
    assertEquals(ImmutableSet.of(), INSTANCE.cellSet());
  }

    protected DocumentBuilderFactoryUtil() {
    }

    /**
     * Returns a new instance of {@link DocumentBuilderFactory}.
     *
     * @return A new instance of {@link DocumentBuilderFactory}.
     */
    public static DocumentBuilderFactory newInstance() {
        return newInstance(false);
    }

    /**
     * Returns a new instance of {@link DocumentBuilderFactory}.
     *
     * @param external

    @Test
    public void test_constructor() {
        assertNotNull(target, "Constructor should create instance");
        assertTrue(target instanceof HotThreadMonitorTarget, "Instance should be of correct type");
        assertTrue(target instanceof MonitorTarget, "Instance should be a MonitorTarget");
        assertTrue(target instanceof TimeoutTarget, "Instance should be a TimeoutTarget");
    }

    @Test

    private TimeoutManager() {
    }

    /**
     * Returns the instance for the singleton.
     *
     * @return the instance for the singleton
     */
    public static TimeoutManager getInstance() {
        return instance;
    }

    /**
     * Starts the process.
     */
    public synchronized void start() {
        if (thread == null) {