Program: 75613
Project: 75613
Buggy source:
public void actionPerformed(ActionEvent e){
  super.actionPerformed(e);
  NamedObj target=getTarget();
  if (!(target instanceof Transition)) {
    MessageHandler.error("String_Node_Str");
    return;
  }
  Transition transition=(Transition)target;
  CompositeEntity immediateContainer=(CompositeEntity)transition.getContainer();
  if (immediateContainer == null) {
    MessageHandler.error("String_Node_Str");
    return;
  }
  final CompositeEntity container=(CompositeEntity)immediateContainer.getContainer();
  if (container == null) {
    MessageHandler.error("String_Node_Str");
    return;
  }
  TypedActor[] refinements;
  try {
    refinements=transition.getRefinement();
  }
 catch (  Exception ex) {
    MessageHandler.error("String_Node_Str",ex);
    return;
  }
  if (refinements == null || refinements.length < 1) {
    MessageHandler.error("String_Node_Str");
    return;
  }
  String[] choices=new String[refinements.length];
  for (int i=0; i < refinements.length; i++) {
    choices[i]=((Nameable)refinements[i]).getName();
  }
  Query query=new Query();
  query.addChoice("String_Node_Str","String_Node_Str",choices,choices[0],false);
  ComponentDialog dialog=new ComponentDialog(null,"String_Node_Str",query);
  if (!dialog.buttonPressed().equals("String_Node_Str")) {
    return;
  }
  String refinementName=query.getStringValue("String_Node_Str");
  StringBuffer newRefinements=new StringBuffer();
  String currentRefinements=transition.refinementName.getExpression();
  StringTokenizer tokenizer=new StringTokenizer(currentRefinements,"String_Node_Str");
  while (tokenizer.hasMoreTokens()) {
    String token=tokenizer.nextToken();
    if (!token.trim().equals(refinementName)) {
      if (newRefinements.length() > 0) {
        newRefinements.append("String_Node_Str");
      }
      newRefinements.append(token.trim());
    }
  }
  Iterator transitions=immediateContainer.entityList().iterator();
  boolean foundOne=false;
  while (transitions.hasNext()) {
    NamedObj other=(NamedObj)transitions.next();
    if (other != transition && other instanceof Transition) {
      String refinementList=((Transition)other).refinementName.getExpression();
      if (refinementList == null)       continue;
      tokenizer=new StringTokenizer(refinementList,"String_Node_Str");
      while (tokenizer.hasMoreTokens()) {
        String token=tokenizer.nextToken();
        if (token.equals(refinementName)) {
          foundOne=true;
          break;
        }
      }
      if (foundOne)       break;
    }
  }
  String removal="String_Node_Str";
  if (!foundOne) {
    removal="String_Node_Str" + refinementName + "String_Node_Str";
  }
  String moml="String_Node_Str" + transition.getName(container) + "String_Node_Str"+ newRefinements.toString()+ "String_Node_Str"+ removal+ "String_Node_Str";
  MoMLChangeRequest change=new MoMLChangeRequest(this,container,moml);
  container.requestChange(change);
}

Fixed version (ground truth):
public void actionPerformed(ActionEvent e){
  super.actionPerformed(e);
  NamedObj target=getTarget();
  if (!(target instanceof Transition)) {
    MessageHandler.error("String_Node_Str");
    return;
  }
  Transition transition=(Transition)target;
  CompositeEntity immediateContainer=(CompositeEntity)transition.getContainer();
  if (immediateContainer == null) {
    MessageHandler.error("String_Node_Str");
    return;
  }
  final CompositeEntity container=(CompositeEntity)immediateContainer.getContainer();
  if (container == null) {
    MessageHandler.error("String_Node_Str");
    return;
  }
  TypedActor[] refinements;
  try {
    refinements=transition.getRefinement();
  }
 catch (  Exception ex) {
    MessageHandler.error("String_Node_Str",ex);
    return;
  }
  if (refinements == null || refinements.length < 1) {
    MessageHandler.error("String_Node_Str");
    return;
  }
  String[] choices=new String[refinements.length];
  for (int i=0; i < refinements.length; i++) {
    choices[i]=((Nameable)refinements[i]).getName();
  }
  Query query=new Query();
  query.addChoice("String_Node_Str","String_Node_Str",choices,choices[0],false);
  ComponentDialog dialog=new ComponentDialog(null,"String_Node_Str",query);
  if (!dialog.buttonPressed().equals("String_Node_Str")) {
    return;
  }
  String refinementName=query.getStringValue("String_Node_Str");
  StringBuffer newRefinements=new StringBuffer();
  String currentRefinements=transition.refinementName.getExpression();
  StringTokenizer tokenizer=new StringTokenizer(currentRefinements,"String_Node_Str");
  while (tokenizer.hasMoreTokens()) {
    String token=tokenizer.nextToken();
    if (!token.trim().equals(refinementName)) {
      if (newRefinements.length() > 0) {
        newRefinements.append("String_Node_Str");
      }
      newRefinements.append(token.trim());
    }
  }
  Iterator transitions=immediateContainer.relationList().iterator();
  boolean foundOne=false;
  while (transitions.hasNext()) {
    NamedObj other=(NamedObj)transitions.next();
    if (other != transition && other instanceof Transition) {
      String refinementList=((Transition)other).refinementName.getExpression();
      if (refinementList == null)       continue;
      tokenizer=new StringTokenizer(refinementList,"String_Node_Str");
      while (tokenizer.hasMoreTokens()) {
        String token=tokenizer.nextToken();
        if (token.equals(refinementName)) {
          foundOne=true;
          break;
        }
      }
      if (foundOne)       break;
    }
  }
  if (!foundOne) {
    Iterator states=immediateContainer.entityList().iterator();
    while (states.hasNext()) {
      NamedObj other=(NamedObj)states.next();
      if (other instanceof State) {
        String refinementList=((State)other).refinementName.getExpression();
        if (refinementList == null)         continue;
        tokenizer=new StringTokenizer(refinementList,"String_Node_Str");
        while (tokenizer.hasMoreTokens()) {
          String token=tokenizer.nextToken();
          if (token.equals(refinementName)) {
            foundOne=true;
            break;
          }
        }
        if (foundOne)         break;
      }
    }
  }
  String removal="String_Node_Str";
  if (!foundOne) {
    removal="String_Node_Str" + refinementName + "String_Node_Str";
  }
  String moml="String_Node_Str" + transition.getName(container) + "String_Node_Str"+ newRefinements.toString()+ "String_Node_Str"+ removal+ "String_Node_Str";
  MoMLChangeRequest change=new MoMLChangeRequest(this,container,moml);
  container.requestChange(change);
}