android/guava/src/com/google/common/collect/Maps.java
public static <K, V> BiMap<K, V> filterKeys(
      BiMap<K, V> unfiltered, final Predicate<? super K> keyPredicate) {
    checkNotNull(keyPredicate);
    return filterEntries(unfiltered, Maps.<K>keyPredicateOnEntries(keyPredicate));
  }
public static <K, V> BiMap<K, V> filterKeys(
      BiMap<K, V> unfiltered, final Predicate<? super K> keyPredicate) {
    checkNotNull(keyPredicate);
    return filterEntries(unfiltered, Maps.<K>keyPredicateOnEntries(keyPredicate));
  }
public static < K , V > BiMap < K , V > filterKeys ( BiMap < K , V > unfiltered , final Predicate < ? super K > keyPredicate ) { checkNotNull ( keyPredicate ) ; return filterEntries ( unfiltered , Maps . < K > keyPredicateOnEntries ( keyPredicate ) ) ; }
Returns a bimap containing the mappings in {@code unfiltered} whose keys satisfy a predicate.
The returned bimap is a live view of {@code unfiltered}; changes to one affect the other.

<p>The resulting bimap's {@code keySet()}, {@code entrySet()}, and {@code values()} views have
iterators that don't support {@code remove()}, but all other methods are supported by the bimap
and its views. When given a key that doesn't satisfy the predicate, the bimap's {@code put()},
{@code forcePut()} and {@code putAll()} methods throw an {@link IllegalArgumentException}.

<p>When methods such as {@code removeAll()} and {@code clear()} are called on the filtered
bimap or its views, only mappings that satisfy the filter will be removed from the underlying
bimap.

<p>The returned bimap isn't threadsafe or serializable, even if {@code unfiltered} is.

<p>Many of the filtered bimap's methods, such as {@code size()}, iterate across every key in
the underlying bimap and determine which satisfy the filter. When a live view is <i>not</i>
needed, it may be faster to copy the filtered bimap and use the copy.

<p><b>Warning:</b> {@code entryPredicate} must be <i>consistent with equals </i>, as documented
at {@link Predicate#apply}.

@since 14.0
Returns a bimap containing the mappings in { @code unfiltered } whose keys satisfy a predicate . The returned bimap is a live view of { @code unfiltered } ; changes to one affect the other .