Java8Compatibility.flip(buf);
      to.append(buf);
      total += buf.remaining();
      Java8Compatibility.clear(buf);
    }
    return total;
  }

  // TODO(lukes): consider allowing callers to pass in a buffer to use, some callers would be able
  // to reuse buffers, others would be able to size them more appropriately than the constant
  // defaults

  /**

mvn formatter:format
mvn license:format
```

### Code Style

- Follow Java coding conventions
- Use proper JavaDoc comments for public APIs
- Include unit tests for new functionality
- Ensure all tests pass before submitting PR

## License

     * then set the result of the computation, and only then transition to COMPLETED, CANCELLED, or
     * INTERRUPTED.
     *
     * <p>We don't use the integer argument passed between acquire methods so we pass around a -1
     * everywhere.
     */
    static final class Sync<V> extends AbstractQueuedSynchronizer {

      private static final long serialVersionUID = 0L;

      /* Valid states. */

     * - Temporarily change this test:
     * --- Comment out assertEquals.
     * --- System.out.println(input + " " + simplifyPath(input));
     * --- fail(). (If the test were to pass, its output would be hidden.)
     * - Run the test.
     * - Pull the relevant lines of output from the test into a testcases file.
     * - Test the output:
     * --- cat testcases | while read L; do

   */

  /*
   * These generators also rely on consecutive integer inputs (not necessarily in order, but no
   * holes).
   */

  // SetCreationTester has some tests that pass in duplicates. Dedup them.
  private static <E extends Comparable<? super E>> SortedSet<E> nullCheckedTreeSet(E[] elements) {
    SortedSet<E> set = newTreeSet();
    for (E element : elements) {

     * - Temporarily change this test:
     * --- Comment out assertEquals.
     * --- System.out.println(input + " " + simplifyPath(input));
     * --- fail(). (If the test were to pass, its output would be hidden.)
     * - Run the test.
     * - Pull the relevant lines of output from the test into a testcases file.
     * - Test the output:
     * --- cat testcases | while read L; do

                    .map(this::resolve)
                    .forEach(paths::add);
        }
        sessionBuilder.withLocalRepositoryBaseDirectories(paths);
        // Pass over property supported by Maven 3.9.x
        if (mergedProps.containsKey(Constants.MAVEN_REPO_LOCAL_TAIL_IGNORE_AVAILABILITY)) {
            configProps.put(

  public final @Nullable V getOrDefault(@Nullable Object key, @Nullable V defaultValue) {
    /*
     * Even though it's weird to pass a defaultValue that is null, some callers do so. Those who
     * pass a literal "null" should probably just use `get`, but I would expect other callers to
     * pass an expression that *might* be null. This could happen with:
     *
     * - a `getFooOrDefault(@Nullable Foo defaultValue)` method that returns

    @Test
    public void test_validateFilePath_noPropertiesSet() throws Exception {
        final FessAdminAction action = createAction();
        // No system properties set - should pass without checking

        final File anyFile = new File(tempDir.toFile(), "any/test.txt");
        anyFile.getParentFile().mkdirs();
        anyFile.createNewFile();

  }

  /**
   * This is adapted from the regex suggested by {@link Double#valueOf(String)} for prevalidating
   * inputs. All valid inputs must pass this regex, but it's semantically fine if not all inputs
   * that pass this regex are valid -- only a performance hit is incurred, not a semantics bug.
   */
  @GwtIncompatible // regular expressions
  static final
  java.util.regex.Pattern