Object o22 = properties.get(KEY1);
        assertEquals(VALUE1, o22);
        for (Map.Entry<String, String> entry : properties.entrySet()) {
            entry.setValue(entry.getValue() + "x");
        }
        Object o21 = properties.get(KEY1);
        assertEquals(VALUE1 + "x", o21);

        baos = new ByteArrayOutputStream();
        properties.save(baos);

            if (fields != null) {
                final Map<String, Object> docMap = fields.entrySet().stream()
                        .collect(Collectors.toMap(Entry<String, DocumentField>::getKey, e -> (Object) e.getValue().getValues()));
                docMap.put(fessConfig.getIndexFieldId(), hit.getId());
                docMap.put(fessConfig.getIndexFieldVersion(), hit.getVersion());

      V newValue = remappingFunction.apply(entry.getValue().getValue(), value);
      if (newValue == null) {
        backingItr.remove();
      } else {
        entry.setValue(
            new RangeMapEntry<K, V>(
                entry.getValue().getLowerBound(), entry.getValue().getUpperBound(), newValue));
      }
    }

    entriesByLowerBound.putAll(gaps.build());
  }

    @Override
    public V getValue() {
      synchronized (mutex) {
        return delegate().getValue();
      }
    }

    @Override
    public V setValue(V value) {
      synchronized (mutex) {
        return delegate().setValue(value);
      }
    }

    private static final long serialVersionUID = 0;
  }

    @Override
    public V getValue() {
      synchronized (mutex) {
        return delegate().getValue();
      }
    }

    @Override
    public V setValue(V value) {
      synchronized (mutex) {
        return delegate().setValue(value);
      }
    }

    private static final long serialVersionUID = 0;
  }

  }

  /**
   * Verifies that {@code key} and {@code value} are non-null, and returns a new immutable entry
   * with those values.
   *
   * <p>A call to {@link Entry#setValue} on the returned entry will always throw {@link
   * UnsupportedOperationException}.
   */
  static <K, V> Entry<K, V> entryOf(K key, V value) {
    return new ImmutableMapEntry<>(key, value);
  }

  /**

    }
    return Collections.unmodifiableCollection(collection);
  }

  /**
   * Returns an unmodifiable view of the specified collection of entries. The {@link Entry#setValue}
   * operation throws an {@link UnsupportedOperationException}. If the specified collection is a
   * {@code Set}, the returned collection is also a {@code Set}.
   *

  }

  /**
   * Verifies that {@code key} and {@code value} are non-null, and returns a new immutable entry
   * with those values.
   *
   * <p>A call to {@link Entry#setValue} on the returned entry will always throw {@link
   * UnsupportedOperationException}.
   */
  static <K, V> Entry<K, V> entryOf(K key, V value) {
    checkEntryNotNull(key, value);