protected synchronized boolean add(Set<String> stackTraceSet,final Throwable throwable){
  if (this.on) {
    String trace=convert(throwable);
    return stackTraceSet.add(trace);
  }
  return false;
}

protected synchronized boolean add ( Set < String > stackTraceSet , final Throwable throwable ) { if ( this . on ) { String trace = convert ( throwable ) ; return stackTraceSet . add ( trace ) ; } return false ; }
adds a stack trace to a collection set if it is unique .
