represent, as a whole, an original work of authorship. For the purposes
      of this License, Derivative Works shall not include works that remain
      separable from, or merely link (or bind by name) to the interfaces of,
      the Work and Derivative Works thereof.

      "Contribution" shall mean any work of authorship, including
      the original version of the Work and any modifications or additions

      represent, as a whole, an original work of authorship. For the purposes
      of this License, Derivative Works shall not include works that remain
      separable from, or merely link (or bind by name) to the interfaces of,
      the Work and Derivative Works thereof.

      "Contribution" shall mean any work of authorship, including
      the original version of the Work and any modifications or additions

     * - Any character between 0x10000 and 0x10FFFF
     *
     * @param in the input string to be processed
     * @return a new string with invalid XML characters removed, or the original
     *         string if it is empty
     */
    public static String stripInvalidXMLCharacters(final String in) {
        if (StringUtil.isEmpty(in)) {
            return in;
        }

1. **Fork** the repository
2. **Create** a feature branch (`git checkout -b feature/amazing-feature`)
3. **Commit** your changes (`git commit -m 'Add amazing feature'`)
4. **Push** to the branch (`git push origin feature/amazing-feature`)
5. **Open** a Pull Request

### Development Setup

```bash
# Clone the repository
git clone https://github.com/codelibs/fess-crawler.git
cd fess-crawler

        final String clusterName = UUID.randomUUID().toString();
        runner.onBuild((number, settingsBuilder) -> {
            settingsBuilder.put("http.cors.enabled", true);
            settingsBuilder.put("http.cors.allow-origin", "*");
            settingsBuilder.put("discovery.type", "single-node");
        }).build(newConfigs().clusterName(clusterName).numOfNode(1));

        // wait for yellow status
        runner.ensureYellow();

            ois.close();

            // Verify - enum instances are singletons
            assertSame(original, deserialized);
            assertEquals(original.name(), deserialized.name());
            assertEquals(original.ordinal(), deserialized.ordinal());
        }
    }

    /**
     * Test EnumSet functionality
     */
    public void test_enumSet() {

        ois.close();

        // Verify
        assertNotNull(deserialized);
        assertEquals(original.getMessage(), deserialized.getMessage());
        assertNotNull(deserialized.getCause());
        assertEquals(original.getCause().getMessage(), deserialized.getCause().getMessage());
        assertEquals(original.getCause().getClass(), deserialized.getCause().getClass());
    }

    /**

        TestAccessResultData<String> original = new TestAccessResultData<>("test data".getBytes());
        original.setUrl("http://example.com");

        // Serialize
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(original);
        oos.close();

        // Deserialize

            this.startOffset = startOffset;
            this.endOffset = endOffset;
            this.posInc = posInc;
            this.output = output;
            this.seq = 0; // zero for seq means that this token is the original of synonyms
        }

        public MyToken(final String word, final int startOffset, final int endOffset, final int posInc) {

4. Add tests for new functionality
5. Ensure all tests pass: `mvn test`
6. Check license headers: `mvn license:format`
7. Commit changes: `git commit -m 'Add amazing feature'`
8. Push to branch: `git push origin feature/amazing-feature`
9. Open a Pull Request

### Code Style

- Use Eclipse formatter configuration (`src/config/eclipse/formatter/java.xml`)
- Follow existing naming conventions