public void makeImmutable(){
  if (!isImmutable) {
    overflowEntries=overflowEntries.isEmpty() ? Collections.<K,V>emptyMap() : Collections.unmodifiableMap(overflowEntries);
    isImmutable=true;
  }
}

public void makeImmutable ( ) { if ( ! isImmutable ) { overflowEntries = overflowEntries . isEmpty ( ) ? Collections . < K , V > emptyMap ( ) : Collections . unmodifiableMap ( overflowEntries ) ; isImmutable = true ; } }
make this map immutable from this point forward .
