push(stack, collector.combiner().apply(left, right));
        }
        return pop(stack);
      }

      <E extends @Nullable Object> void push(List<E> stack, E value) {
        stack.add(value);
      }

      <E extends @Nullable Object> E pop(List<E> stack) {
        return stack.remove(stack.size() - 1);
      }
    };

    }

    @Override
    public boolean containsKey(Object key) {
      return standardContainsKey(key);
    }

    @Override
    public boolean containsValue(Object value) {
      return standardContainsValue(value);
    }

    @Override
    public void putAll(Map<? extends K, ? extends V> map) {
      standardPutAll(map);
    }

    @Override
    public @Nullable V remove(Object object) {

 *
 * <p>Note to maintainers: This implementation relies on signed arithmetic being bit-wise equivalent
 * to unsigned arithmetic in all cases except:
 *
 * <ul>
 *   <li>comparisons (signed values can be negative)
 *   <li>division (avoided here)
 *   <li>shifting (right shift must be unsigned)
 * </ul>
 *
 * @author ******@****.*** (Kyle Maddison)
 * @author ******@****.*** (Geoff Pike)
 */

        assertFalse(mockService.unregisterWitness("non-existent"));
        assertFalse(mockService.processHeartbeat("non-existent", 1));

        // Test registration with null/empty values
        String regId1 = mockService.registerWitness(null, "192.168.1.100", 1);
        assertNotNull(regId1);

        String regId2 = mockService.registerWitness("", "192.168.1.100", 1);
        assertNotNull(regId2);

    return predicate.apply(immutableEntry(key, value));
  }

  final class ValuePredicate implements Predicate<V> {
    @ParametricNullness private final K key;

    ValuePredicate(@ParametricNullness K key) {
      this.key = key;
    }

    @Override
    public boolean apply(@ParametricNullness V value) {
      return satisfies(key, value);
    }
  }

                    return true;
                }
                return false;
            });

            // Persist all persistent handles
            for (HandleInfo info : handles.values()) {
                if (info.getType() == HandleType.PERSISTENT && !info.isReconnecting()) {
                    persistHandle(info);
                }
            }
        } finally {

    // Helper: reflectively set private/protected field on an object
    private static void setField(Object target, Class<?> declaring, String name, Object value) {
        try {
            Field f = declaring.getDeclaredField(name);
            f.setAccessible(true);
            f.set(target, value);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    // Simple FileEntry stub for tests

## Decoding Metadata

Metadata is stored in `xl.meta` files for erasure coded objects. Each disk in the set containing the object has this file. The file format is a binary format and therefore requires tools to view values.

### Installing xl-meta

To install, [Go](https://golang.org/dl/) must be installed. Once installed, execute this to install the binary:

```bash
go install github.com/minio/minio/docs/debugging/xl-meta@latest

type Metadata struct {
	Items []struct {
		Key   string
		Value string
	}
}

// Set add items, duplicate items get replaced.
func (s *Metadata) Set(k, v string) {
	for i, item := range s.Items {
		if item.Key == k {
			s.Items[i] = struct {
				Key   string
				Value string
			}{
				Key:   k,
				Value: v,
			}
			return
		}
	}
	s.Items = append(s.Items, struct {

         * The number of sub-authorities in this SID.
         */
        public byte sub_authority_count;
        /**
         * The identifier authority value (6 bytes).
         */
        public byte[] identifier_authority;
        /**
         * Array of sub-authority values.
         */
        public int[] sub_authority;

        @Override
        public void encode(NdrBuffer _dst) throws NdrException {