* {@link Multimap} itself). Prefer subtypes such as {@link ImmutableSetMultimap} or {@link
 * ImmutableListMultimap}, which have well-defined {@link #equals} semantics, thus avoiding a common
 * source of bugs and confusion.
 *
 * <p><b>Note:</b> every {@link ImmutableMultimap} offers an {@link #inverse} view, so there is no
 * need for a distinct {@code ImmutableBiMultimap} type.
 *

 * {@link Multimap} itself). Prefer subtypes such as {@link ImmutableSetMultimap} or {@link
 * ImmutableListMultimap}, which have well-defined {@link #equals} semantics, thus avoiding a common
 * source of bugs and confusion.
 *
 * <p><b>Note:</b> every {@link ImmutableMultimap} offers an {@link #inverse} view, so there is no
 * need for a distinct {@code ImmutableBiMultimap} type.
 *

   *       com.google.common.base.Joiner#skipNulls}.
   * </ul>
   *
   * <p>Note that constructors taking a builder object cannot be tested effectively because
   * semantics of builder can be arbitrarily complex. Still, a factory class can be created in the
   * test to facilitate equality testing. For example:
   *
   * <pre>
   * public class FooTest {
   *

   * efficiency. The base class implementation determines successive Unicode code points and invokes
   * {@link #escape(int)} for each of them. If the semantics of your escaper are such that code
   * points in the supplementary range are either all escaped or all unescaped, this method can be
   * implemented more efficiently using {@link CharSequence#charAt(int)}.
   *

 *   {@literal @Override} public int hashCode() {...}
 *   ...
 * }
 * </pre>
 *
 * <p>No cascading checks are performed against the return values of methods unless the method is a
 * static factory method. Neither are semantics of mutation methods such as {@code
 * someList.add(obj)} checked. For more detailed discussion of supported and unsupported cases, see
 * {@link #testEquals}, {@link #testNulls} and {@link #testSerializable}.
 *

 *   {@literal @Override} public int hashCode() {...}
 *   ...
 * }
 * </pre>
 *
 * <p>No cascading checks are performed against the return values of methods unless the method is a
 * static factory method. Neither are semantics of mutation methods such as {@code
 * someList.add(obj)} checked. For more detailed discussion of supported and unsupported cases, see
 * {@link #testEquals}, {@link #testNulls} and {@link #testSerializable}.
 *

   * in the presence of LegacyConverter, at least in the case of users who view the converter as a
   * Function<A, B> or who call convertAll (and for any checkers that apply @PolyNull-like semantics
   * to Converter.convert). So maybe we don't want to think too hard about how to prevent our
   * checkers from issuing errors related to LegacyConverter, since it turns out that

    MathPreconditions.checkNonNegative("tolerance", tolerance);
    return Math.copySign(a - b, 1.0) <= tolerance
        // copySign(x, 1.0) is a branch-free version of abs(x), but with different NaN semantics
        || (a == b) // needed to ensure that infinities equal themselves
        || (Double.isNaN(a) && Double.isNaN(b));
  }

  /**

 * reentrant, so a thread may enter a monitor any number of times, and then must leave the same
 * number of times. The <i>enter</i> and <i>leave</i> operations have the same synchronization
 * semantics as the built-in Java language synchronization primitives.
 *
 * <p>A call to any of the <i>enter</i> methods with <b>void</b> return type should always be

   * same order. (It is guaranteed to return true for instances constructed from the same values in
   * the same order if {@code strictfp} is in effect, or if the system architecture guarantees
   * {@code strictfp}-like semantics.)
   */
  @Override
  public boolean equals(@CheckForNull Object obj) {
    if (obj == null) {
      return false;
    }
    if (getClass() != obj.getClass()) {
      return false;
    }