return null;
        }).when(smbTree).close();

        smbTree.close();

        verify(smbTree).close();
    }

    /**
     * Test for unwrap preserving type safety.
     * Verifies that unwrap maintains type safety at compile time.
     */
    @Test
    void testUnwrap_typeSafety() {
        CustomSmbTree customTree = mock(CustomSmbTree.class);

            return entryIterator.hasNext();
          }

          @Override
          public K next() {
            Entry<K, V> entry = entryIterator.next(); // store local reference for thread-safety
            cacheEntry = entry;
            return entry.getKey();
          }
        };
      }

      @Override
      public int size() {
        return backingMap.size();
      }

        // Null-safety: return null for blank templates
        // Early return is safe here as no resources have been allocated yet
        if (StringUtil.isBlank(template)) {
            if (logger.isDebugEnabled()) {
                logger.debug("Template is blank, returning null");
            }
            return null;
        }

        // Null-safety: use empty map if paramMap is null

If one or more drives are offline at the start of a PutObject or NewMultipartUpload operation the object will have additional data
protection bits added automatically to provide the regular safety for these objects up to 50% of the number of drives.
This will allow normal write operations to take place on systems that exceed the write tolerance.

    .error(throwable -> { /* handle error */ });
```

---

## Important Notes

### Thread Safety
- **Suggester**: Thread-safe for queries
- **SuggestIndexer**: Thread-safe for indexing
- **SuggestSettings**: NOT thread-safe for modifications

### Performance
- Use batch operations for indexing (100-500 items)
- Don't call `refresh()` too frequently

- **Cross-Language Compatibility:**
Java serialization is inherently Java-centric and does not support cross-language scenarios well.

- **Type Safety:**
Java serialization does not enforce type safety as strictly as some alternatives, potentially leading to runtime errors.

## Decision

We do not use Java serialization.

 * <p>
 * <strong>Thread-Safety:</strong> This class is <strong>NOT thread-safe</strong>.
 * It extends {@link LinkedHashMap} without synchronization. If multiple threads access
 * an instance concurrently, and at least one thread modifies the map structurally,
 * it must be synchronized externally.
 * </p>
 * <p>
 * For thread-safe usage, wrap with {@link java.util.Collections#synchronizedMap(Map)}:
 * </p>

**Template Method**: `AbstractCrawlerClient`, `AbstractExtractor` - common logic with overrides
**DI**: LastaFlute container with `@Resource` and XML config

### Core Principles

**Thread Safety**:
- `AtomicLong` for counters (`CrawlerContext.accessCount`)
- `volatile` for status flags
- Synchronized blocks for critical sections
- Thread-local storage via `CrawlingParameterUtil`

**Resource Management**:

import org.dbflute.utflute.core.PlainTestCase;

/**
 * Test class for {@link Handler} and its inner class {@link Handler.GcsURLConnection}.
 * This test covers URL parsing, connection state management, and thread-safety.
 */
public class HandlerTest extends PlainTestCase {
    @Override
    protected void setUp() throws Exception {
        super.setUp();
        new StandardCrawlerContainer();
    }

    /**

    Set<E> result = super.convertToHashFloodingResistantImplementation();
    this.predecessor = null;
    this.successor = null;
    return result;
  }

  /*
   * For discussion of the safety of the following methods for operating on predecessors and
   * successors, see the comments near the end of CompactHashMap, noting that the methods here call