/guava/guava/src/com/google/common/collect/AbstractMapBasedMultimap.java
collection = createCollection( key) ;Collection<V> collection = map.get( key) ;
Collection<V> collection = map.get ( key ) ;
@Override public boolean containsKey(@CheckForNull Object key) { return map.containsKey(key); } @Override public boolean put(@ParametricNullness K key, @ParametricNullness V value) { <extra_id_0> if (collection == null) { collection = createCollection(key); if (collection.add(value)) { totalSize++; map.put(key, collection); return true;