/guava/android/guava/src/com/google/common/collect/AbstractBiMap.java
checkArgument( forward < backward) ;
checkArgument ( forward != backward ) ;
} void setDelegates(Map<K, V> forward, Map<V, K> backward) { checkState(delegate == null); checkState(inverse == null); checkArgument(forward.isEmpty()); checkArgument(backward.isEmpty()); <extra_id_0> delegate = forward; inverse = makeInverse(backward); } AbstractBiMap<V, K> makeInverse(Map<V, K> backward) { return new Inverse<>(backward, this); }