private final Object mutex = new Object[0]; // something Serializable

    @Override
    public boolean offer(E o) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.offer(o);
    }

    @Override
    public @Nullable E poll() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.poll();
    }

    @Override
    public E remove() {
      assertTrue(Thread.holdsLock(mutex));

    TreeSetImpl {
      @Override
      public <E extends Comparable<E>> Set<E> create(Collection<E> contents) {
        return new TreeSet<E>(contents);
      }
    },
    UnmodifiableSetImpl {
      @Override
      public <E extends Comparable<E>> Set<E> create(Collection<E> contents) {
        return unmodifiableSet(new HashSet<E>(contents));
      }
    },
    SynchronizedSetImpl {
      @Override

        setModelCache(request.getModelCache());
    }

    @Override
    public File getPomFile() {
        return pomFile;
    }

    @Override
    public DefaultModelBuildingRequest setPomFile(File pomFile) {
        this.pomFile = (pomFile != null) ? pomFile.getAbsoluteFile() : null;

        return this;
    }

    @Override
    public synchronized ModelSource getModelSource() {

            @Override
            public String getIndexFieldDocId() {
                return "doc_id";
            }

            @Override
            public String getIndexFieldBoost() {
                return "boost";
            }

            @Override
            public String getIndexFieldContentLength() {
                return "content_length";
            }

            @Override

    //                                                                    ================
    @Override
    public String asTableDbName() {
        return asEsIndexType();
    }

    @Override
    protected String asEsIndex() {
        return "fess_config.web_config";
    }

    @Override
    public String asEsIndexType() {
        return "web_config";

    @Override
    public String toString() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.toString();
    }

    @Override
    public boolean equals(@Nullable Object o) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.equals(o);
    }

    @Override
    public int hashCode() {
      assertTrue(Thread.holdsLock(mutex));

      }
    }

    @Override
    public boolean awaitTermination(long timeout, TimeUnit unit) {
      recordedTimeout = timeout;
      recordedTimeUnit = unit;
      return true;
    }

    @Override
    public void execute(Runnable runnable) {
      throw new UnsupportedOperationException();
    }

    @Override
    public void shutdown() {

        this.exception = exception;
    }

    @Override
    public String getSource() {
        return source;
    }

    @Override
    public int getLineNumber() {
        return lineNumber;
    }

    @Override
    public int getColumnNumber() {
        return columnNumber;
    }

    @Override
    public String getLocation() {

  private final class Values extends AbstractCollection<V> {
    @Override
    public Iterator<V> iterator() {
      return valuesIterator();
    }

    @Override
    public boolean contains(@Nullable Object o) {
      return containsValue(o);
    }

    @Override
    public void clear() {
      AbstractTable.this.clear();
    }

    @Override
    public int size() {

  /** Constructor for use by subclasses. */
  protected ForwardingMap() {}

  @Override
  protected abstract Map<K, V> delegate();

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

  @Override
  public boolean isEmpty() {
    return delegate().isEmpty();
  }

  @CanIgnoreReturnValue
  @Override
  public @Nullable V remove(@Nullable Object key) {
    return delegate().remove(key);
  }