public void add(final Object element){
  Set oldSelection=new HashSet(selection);
  boolean rv=selection.add(element);
  if (rv) {
    fireSelectionChanged(oldSelection,selection);
  }
  oldSelection=null;
}

public void add ( final Object element ) { Set oldSelection = new HashSet ( selection ) ; boolean rv = selection . add ( element ) ; if ( rv ) { fireSelectionChanged ( oldSelection , selection ) ; } oldSelection = null ; }
add the specified element to the selection .
