private Synchronization localPopSynchronization(){
  Synchronization ret=null;
  if (!synchronizations_.isEmpty())   ret=synchronizations_.pop();
  return ret;
}

private Synchronization localPopSynchronization ( ) { Synchronization ret = null ; if ( ! synchronizations_ . isEmpty ( ) ) ret = synchronizations_ . pop ( ) ; return ret ; }
should be called instead of iterator : commit can add more synchronizations so an iterator would give concurrentmodificationexception !
