}

  static CommonPattern compilePattern(String pattern) {
    Preconditions.checkNotNull(pattern);
    return patternCompiler.compile(pattern);
  }

  static boolean patternCompilerIsPcreLike() {
    return patternCompiler.isPcreLike();
  }

  private static PatternCompiler loadPatternCompiler() {
    // We want the JDK Pattern compiler:
    // - under Android (where it hurts startup performance)

    @ParametricNullness
    @SuppressWarnings("unchecked") // Cast from Supplier<Void> to Supplier<T> is always valid
    public T get() {
      // Because Supplier is read-heavy, we use the "double-checked locking" pattern.
      if (delegate != SUCCESSFULLY_COMPUTED) {
        synchronized (lock) {
          if (delegate != SUCCESSFULLY_COMPUTED) {
            T t = delegate.get();
            value = t;

                    logger.debug("Using exclude pattern: {}", pattern);
                }
            }
            if (paramMap.get(URL_EXCLUDE_PATTERN) instanceof final Pattern pattern) {
                if (pattern.matcher(url).matches()) {
                    if (logger.isDebugEnabled()) {
                        logger.debug("Skipping URL {} due to exclude pattern: {}", url, pattern);
                    }
                    return false;

        .containsExactly("Testing", "rocks", "Debugging", "sucks")
        .inOrder();
  }

  @GwtIncompatible // java.util.regex.Pattern
  private static Pattern literalDotPattern() {
    return Pattern.compile("\\.");
  }

  @GwtIncompatible // java.util.regex.Pattern
  public void testPatternSplitWithDoubleDelimiterOmitEmptyStrings() {
    String doubled = "a..b.c";

        StopwordsItem item4 = new StopwordsItem(1, "different");

        // Same object
        assertTrue(item1.equals(item1));

        // Same input value (id doesn't matter)
        assertTrue(item1.equals(item2));
        assertTrue(item1.equals(item3));

        // Different input value
        assertFalse(item1.equals(item4));

        // Null and different class

     * shouldn't)
     *
     * Our solution is for threads to CAS seenExceptionsField from null to a Set populated with _the
     * initial exception_, no matter which thread does the work. This ensures that
     * seenExceptionsField always contains not just the current thread's exception but also the
     * initial thread's.
     */

        // This will make sure that tasks don't get stuck busy waiting.
        // Some of this is fixed in jdk11 (see https://bugs.openjdk.org/browse/JDK-8198692) but
        // not all.  See the test cases for examples on how this can happen.
        try {
          ((Thread) currentRunner).interrupt();
        } finally {
          Runnable prev = getAndSet(DONE);
          if (prev == PARKED) {
            LockSupport.unpark((Thread) currentRunner);

     * This cache improves performance by avoiding repeated parsing of client configuration rules.
     * The key is the rule string, and the value is a pair containing the client name and compiled pattern.
     */
    protected ConcurrentHashMap<String, Pair<String, Pattern>> clientRuleCache = new ConcurrentHashMap<>();

    /**
     * Determines whether the content at the given URL has been updated since the last crawl.

### Key Architectural Patterns
- **Factory Pattern** - `BeanDescFactory` for creating bean descriptors, `ParameterizedClassDescFactory` for generic type handling
- **Builder Pattern** - `CopyOptions` for configuring bean copying operations with fluent API
- **Adapter Pattern** - Logging adapters (`JclLoggerAdapter`, `JulLoggerAdapter`) for different logging frameworks

   * when we use a newer -source and -target. That doesn't normally matter for AbstractFutureState,
   * since Android should normally succed in using UnsafeAtomicHelper and thus never even try the
   * problematic AtomicReferenceFieldUpdaterAtomicHelper code path. However, the same problem *does*
   * matter with AggregateFutureState, which does not have an Unsafe-based helper.
   *