Program: 75223
Project: 75223
Buggy source:
/** 
 * Read one token from the input. If the value of the input is bigger than 0.0, save the input to be processed in the postfire method. Otherwise,  check whether there is any output scheduled to be produced at the  current time. If there is one, send out that output and save the  current input for future processing in the postfire method. If there  is no output to produce, the timer is not processing other inputs, and the input value is 0.0, send an output immediately and reset the  current input to null, indicating no further processing of the current  input is necessary.
 * @exception IllegalActionException If there is no director, or can notsend or get tokens from ports.
 */
public void fire() throws IllegalActionException {
  _delay=-1.0;
  if (input.hasToken(0)) {
    _currentInput=input.get(0);
    _delayedInputTokensList.addLast(_currentInput);
    double delayValue=((DoubleToken)_currentInput).doubleValue();
    if (delayValue < 0) {
      throw new IllegalActionException("String_Node_Str");
    }
 else {
      _delay=delayValue;
    }
  }
 else {
    _currentInput=null;
  }
  Time currentTime=getDirector().getModelTime();
  _currentOutput=null;
  if (_delayedTokens.size() > 0) {
    _currentOutput=(Token)_delayedTokens.get(currentTime);
    if (_currentOutput != null) {
      output.send(0,value.getToken());
      return;
    }
 else {
    }
  }
 else   if (_delay == 0.0 && _delayedInputTokensList.size() > 0) {
    _delayedInputTokensList.removeFirst();
    output.send(0,value.getToken());
    _currentInput=null;
  }
}

Fixed version (ground truth):
/** 
 * Read one token from the input. If the value of the input is bigger than 0.0, save the input to be processed in the postfire method. Otherwise,  check whether there is any output scheduled to be produced at the  current time. If there is one, send out that output and save the  current input for future processing in the postfire method. If there  is no output to produce, the timer is not processing other inputs, and the input value is 0.0, send an output immediately and reset the  current input to null, indicating no further processing of the current  input is necessary.
 * @exception IllegalActionException If there is no director, or can notsend or get tokens from ports.
 */
public void fire() throws IllegalActionException {
  _delay=-1.0;
  if (input.hasToken(0)) {
    _currentInput=input.get(0);
    _delayedInputTokensList.addLast(_currentInput);
    double delayValue=((DoubleToken)_currentInput).doubleValue();
    if (delayValue < 0) {
      throw new IllegalActionException("String_Node_Str");
    }
 else {
      _delay=delayValue;
    }
  }
 else {
    _currentInput=null;
  }
  Time currentTime=getDirector().getModelTime();
  _currentOutput=null;
  if (_delayedOutputTokens.size() > 0) {
    if (currentTime.compareTo(_nextTimeFree) == 0) {
      TimedEvent earliestEvent=(TimedEvent)_delayedOutputTokens.get();
      Time eventTime=earliestEvent.timeStamp;
      if (!eventTime.equals(currentTime)) {
        throw new InternalErrorException("String_Node_Str" + "String_Node_Str");
      }
      _currentOutput=(Token)earliestEvent.contents;
      output.send(0,_currentOutput);
      return;
    }
 else {
    }
  }
 else   if (_delay == 0.0 && _delayedInputTokensList.size() > 0) {
    _delayedInputTokensList.removeFirst();
    output.send(0,value.getToken());
    _currentInput=null;
  }
}