}

    /**
     * Throws {@link UnsupportedOperationException}. This method is inherited from {@link
     * ImmutableMap.Builder}, but it does not make sense for bimaps.
     *
     * @throws UnsupportedOperationException always
     * @deprecated This method does not make sense for bimaps and should not be called.
     * @since 31.1
     */
    @DoNotCall
    @Deprecated
    @Override

     *   `map.getOrDefault(FOO_KEY, defaultValue)`
     *
     * - a call that consults a chain of maps, as in `mapA.getOrDefault(key, mapB.getOrDefault(key,
     *   ...))`
     *
     * So it makes sense for the parameter (and thus the return type) to be @CheckForNull.
     *
     * Two other points:
     *
     * 1. We'll want to use something like @PolyNull once we can make that work for the various

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A comparator, with additional methods to support common operations. This is an "enriched" version
 * of {@code Comparator} for pre-Java-8 users, in the same sense that {@link FluentIterable} is an
 * enriched {@link Iterable} for pre-Java-8 users.
 *
 * <h3>Three types of methods</h3>
 *
 * Like other fluent types, there are three types of methods present: methods for <i>acquiring</i>,