question: public void addExceptionalSuccessor ( BlockImpl b , TypeMirror cause ) { if ( exceptionalSuccessors == null ) { exceptionalSuccessors = new HashMap < > ( ) ; } Set < Block > blocks = exceptionalSuccessors . get ( cause ) ; if ( blocks == null ) { blocks = new HashSet < Block > ( ) ; exceptionalSuccessors . put ( cause , blocks ) ; } blocks . add ( b ) ; b . addPredecessor ( this ) ; }
target:  Add an exceptional successor.