public synchronized Object put ( Object key , Object value ) throws NullPointerException { if ( key == null || value == null ) throw new NullPointerException ( ) ; int index = keys . indexOf ( key ) ; if ( index != - 1 ) { Object prev = elements . elementAt ( index ) ; elements . setElementAt ( value , index ) ; return prev ; } else { keys . addElement ( key ) ; elements . addElement ( value ) ; return null ; } }
Maps the specified key to the specified value in this table .