question: public synchronized < T extends EventListener > void add ( Class < T > t , T l ) { if ( l == null ) { return ; } if ( ! t . isInstance ( l ) ) { throw new IllegalArgumentException ( "Listener " + l + " is not of type " + t ) ; } if ( listenerList == NULL_ARRAY ) { listenerList = new Object [ ] { t , l } ; } else { int i = listenerList . length ; Object [ ] tmp = new Object [ i + 2 ] ; System . arraycopy ( listenerList , 0 , tmp , 0 , i ) ; tmp [ i ] = t ; tmp [ i + 1 ] = l ; listenerList = tmp ; } }
target:  Adds the listener as a listener of the specified type.