final HashBiMap<K, V> obverse;

    Inverse(HashBiMap<K, V> obverse) {
      this.obverse = obverse;
    }

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

    @Override
    public boolean containsKey(@Nullable Object key) {
      Object obverseValue = key;
      return obverse.containsValue(obverseValue);
    }

    @Override

    /* No aliasing on inverse operations. */
    assertSame(unmod.inverse(), unmod.inverse());
    assertSame(unmod, unmod.inverse().inverse());

    /* Unmodifiable is a view. */
    mod.put(4, "four");
    assertEquals(true, unmod.get(4).equals("four"));
    assertEquals(true, unmod.inverse().get("four").equals(4));

    /* No aliasing on inverse operations. */
    assertSame(unmod.inverse(), unmod.inverse());
    assertSame(unmod, unmod.inverse().inverse());

    /* Unmodifiable is a view. */
    mod.put(4, "four");
    assertEquals(true, unmod.get(4).equals("four"));
    assertEquals(true, unmod.inverse().get("four").equals(4));

  public abstract ImmutableCollection<V> get(K key);

  /**
   * Returns an immutable multimap which is the inverse of this one. For every key-value mapping in
   * the original, the result will have a mapping with key and value reversed.
   *
   * @since 11.0
   */
  public abstract ImmutableMultimap<V, K> inverse();

  /**
   * Guaranteed to throw an exception and leave the multimap unmodified.
   *

  public abstract ImmutableCollection<V> get(K key);

  /**
   * Returns an immutable multimap which is the inverse of this one. For every key-value mapping in
   * the original, the result will have a mapping with key and value reversed.
   *
   * @since 11.0
   */
  public abstract ImmutableMultimap<V, K> inverse();

  /**
   * Guaranteed to throw an exception and leave the multimap unmodified.
   *

    Converter<String, TestEnum> converter = Enums.stringConverter(TestEnum.class);
    assertEquals("CHEETO", converter.reverse().convert(TestEnum.CHEETO));
    assertEquals("HONDA", converter.reverse().convert(TestEnum.HONDA));
    assertEquals("POODLE", converter.reverse().convert(TestEnum.POODLE));
  }

  @J2ktIncompatible
  public void testStringConverter_nullPointerTester() throws Exception {

    assertThat(Ints.stringConverter().reverse().convert(null)).isNull();
  }

  public void testStringConverter_reverse() {
    Converter<String, Integer> converter = Ints.stringConverter();
    assertThat(converter.reverse().convert(1)).isEqualTo("1");
    assertThat(converter.reverse().convert(0)).isEqualTo("0");
    assertThat(converter.reverse().convert(-1)).isEqualTo("-1");

    assertThat(Shorts.stringConverter().reverse().convert(null)).isNull();
  }

  public void testStringConverter_reverse() {
    Converter<String, Short> converter = Shorts.stringConverter();
    assertThat(converter.reverse().convert((short) 1)).isEqualTo("1");
    assertThat(converter.reverse().convert((short) 0)).isEqualTo("0");
    assertThat(converter.reverse().convert((short) -1)).isEqualTo("-1");

    assertThat(Doubles.stringConverter().reverse().convert(null)).isNull();
  }

  @GwtIncompatible // Double.toString returns different value in GWT.
  public void testStringConverter_reverse() {
    Converter<String, Double> converter = Doubles.stringConverter();
    assertThat(converter.reverse().convert(1.0)).isEqualTo("1.0");
    assertThat(converter.reverse().convert(0.0)).isEqualTo("0.0");

    input = Arrays.copyOf(input, input.length);
    Chars.reverse(input);
    assertThat(input).isEqualTo(expectedOutput);
  }

  private static void testReverse(char[] input, int fromIndex, int toIndex, char[] expectedOutput) {
    input = Arrays.copyOf(input, input.length);
    Chars.reverse(input, fromIndex, toIndex);
    assertThat(input).isEqualTo(expectedOutput);
  }