private ArrayList<Interval> findOrCreateIntervalSet(Register r){
  ArrayList<Interval> v=map.get(r);
  if (v == null) {
    v=new ArrayList<Interval>();
    map.put(r,v);
  }
  return v;
}

private ArrayList < Interval > findOrCreateIntervalSet ( Register r ) { ArrayList < Interval > v = map . get ( r ) ; if ( v == null ) { v = new ArrayList < Interval > ( ) ; map . put ( r , v ) ; } return v ; }
find or create the set of intervals corresponding to a register r .
