@Override public void beforeFirst(){
  currentScan=null;
  s1.beforeFirst();
  hasMore1=s1.next();
  if (s2 != null) {
    s2.beforeFirst();
    hasMore2=s2.next();
  }
}

@ Override public void beforeFirst ( ) { currentScan = null ; s1 . beforeFirst ( ) ; hasMore1 = s1 . next ( ) ; if ( s2 != null ) { s2 . beforeFirst ( ) ; hasMore2 = s2 . next ( ) ; } }
positions the scan before the first record in sorted order . internally , it moves to the first record of each underlying scan . the variable currentscan is set to null , indicating that there is no current scan .
