Hash {
      @Override
      Map<Element, Element> create(Collection<Element> keys) {
        Map<Element, Element> map = Maps.newHashMap();
        for (Element element : keys) {
          map.put(element, element);
        }
        return map;
      }
    },
    LinkedHM {
      @Override
      Map<Element, Element> create(Collection<Element> keys) {
        Map<Element, Element> map = Maps.newLinkedHashMap();

  }

  /**
   * Returns {@code element} cast to {@code E}, if it actually is a nonnull E. Otherwise, throws
   * either a NullPointerException or a ClassCastException as appropriate.
   */
  private void checkIsE(Object element) {
    checkNotNull(element);
    if (!isActuallyE(element)) {
      throw new ClassCastException("Expected an " + type + " but got " + element);
    }
  }

  @Override

    Hash {
      @Override
      Map<Element, Element> create(Collection<Element> keys) {
        Map<Element, Element> map = Maps.newHashMap();
        for (Element element : keys) {
          map.put(element, element);
        }
        return map;
      }
    },
    LinkedHM {
      @Override
      Map<Element, Element> create(Collection<Element> keys) {
        Map<Element, Element> map = Maps.newLinkedHashMap();

    }

    /**
     * {@link Element}を文字列に変換します。
     *
     * @param element
     *            要素。{@literal null}であってはいけません
     * @return 変換された文字列
     */
    public static String toString(final Element element) {
        assertArgumentNotNull("element", element);

        final StringBuilder buf = new StringBuilder(1000);
        appendElement(element, buf);
        return new String(buf);
    }

    if (element instanceof Entry) {
      Entry<?, ?> entry = (Entry<?, ?>) element;
      element = mapEntry(entry.getKey(), entry.getValue());
    }
    assertTrue(collection.contains(element)); // sanity check
    iterator.remove();
    assertFalse(collection.contains(element));
    assertEquals(originalSize - 1, collection.size());
  }

                for (Plugin element : tgt) {
                    Object key = getPluginKey().apply(element);
                    Plugin existing = master.get(key);
                    if (existing != null) {
                        element = mergePlugin(element, existing, sourceDominant, context);

                        master.put(key, element);

                        if (!pending.isEmpty()) {

    }

    /**
     * Adds {@code element} to the {@code ImmutableSortedMultiset}.
     *
     * @param element the element to add
     * @return this {@code Builder} object
     * @throws NullPointerException if {@code element} is null
     */
    @CanIgnoreReturnValue
    @Override
    public Builder<E> add(E element) {
      return addCopies(element, 1);
    }

    /**

      return standardAddAll(collection);
    }

    @Override
    public boolean add(T element) {
      return standardAdd(element);
    }

    @Override
    public void clear() {
      standardClear();
    }

    @Override
    public int count(Object element) {
      return standardCount(element);
    }

    @Override
    public boolean contains(Object object) {

    assertEquals("Should be able to peek() at first element", "A", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() first element multiple times", "A", peekingIterator.peek());
    assertEquals(
        "next() should still return first element after peeking", "A", peekingIterator.next());

    assertEquals("Should be able to peek() at middle element", "B", peekingIterator.peek());
    assertEquals(

  @Override
  void setCountCheckReturnValue(E element, int count) {
    assertEquals(
        "multiset.setCount() should return the old count",
        getMultiset().count(element),
        setCount(element, count));
  }

  @Override
  void setCountNoCheckReturnValue(E element, int count) {
    setCount(element, count);
  }

  @CanIgnoreReturnValue
  private int setCount(E element, int count) {