public Set<K> keySet() {
        if (keySet == null) {
            keySet = new KeySet<K, V>(this);
        }
        return keySet;
    }
public Set<K> keySet() {
        if (keySet == null) {
            keySet = new KeySet<K, V>(this);
        }
        return keySet;
    }
public Set < K > keySet ( ) { if ( keySet == null ) { keySet = new KeySet < K , V > ( this ) ; } return keySet ; }
Gets the keySet view of the map. Changes made to the view affect this
map. To simply iterate through the keys, use {@link #mapIterator()}.

@return the keySet view
Gets the keySet view of the map . Changes made to the view affect this map . To simply iterate through the keys use { @link #mapIterator () } .