question: @ Override public V put ( K key , V value ) { if ( key == null ) return putForNullKey ( value ) ; int hash = hash ( key ) ; int i = indexFor ( hash , table . length ) ; for ( Entry < K , V > e = table [ i ] ; e != null ; e = e . next ) { Object k ; if ( e . hash == hash && ( ( k = e . key ) == key || key . equals ( k ) ) ) { V oldValue = e . value ; e . value = value ; e . recordAccess ( this ) ; return oldValue ; } } modCount ++ ; addEntry ( hash , key , value , i ) ; return null ; }
target:  Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced.