/guava/guava/src/com/google/common/collect/Synchronized.java
return delegate( ).put( key, value) ;keySet = set( delegate( ).keySet( ) , mutex) ;
keySet = set ( delegate ( ) .keySet ( ) , mutex ) ;
} } @Override public Set<K> keySet() { synchronized (mutex) { if (keySet == null) { <extra_id_0> } return keySet; } } @Override @CheckForNull