* - 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

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

     * This method handles different file types (files, directories, symbolic links)
     * and populates the response data accordingly.
     *
     * @param uri The original URI being accessed
     * @param includeContent Whether to include the actual content in the response
     * @param responseData The response data to update
     * @param client The FTP client used for the operation