question: public boolean add ( AccessibleState state ) { if ( states == null ) { states = new Vector ( ) ; } if ( ! states . contains ( state ) ) { states . addElement ( state ) ; return true ; } else { return false ; } }
target:  Adds a new state to the current state set if it is not already present.  If the state is already in the state set, the state set is unchanged and the return value is false.  Otherwise, the state is added to the state set and the return value is true.