@GwtCompatible
/*
 * The type parameter is <T> rather than <T extends @Nullable> so that we can use T in the
 * doEquivalent and doHash methods to indicate that the parameter cannot be null.
 */
@SuppressWarnings("UngroupedOverloads")
public abstract class Equivalence<T> {
  /** Constructor for use by subclasses. */
  protected Equivalence() {}

  /**
   * Returns {@code true} if the given objects are considered equivalent.
   *