Program: 117702
Project: 117702
Buggy source:
protected void populateDirectiveList(){
  DefaultTreeModel treeModel=(DefaultTreeModel)directivesTree.getModel();
  DefaultMutableTreeNode root=new DefaultMutableTreeNode("String_Node_Str");
  DefaultMutableTreeNode other=new DefaultMutableTreeNode("String_Node_Str");
  DirectiveManager directiveManager=DirectiveManager.getDirectiveManager();
  List<Class<? extends Directive>> directives=directiveManager.getDirectives();
  List<DirectiveUIHints> hints=new ArrayList<>();
  for (  Class<? extends Directive> dir : directives) {
    DirectiveUIHints h=DirectiveUIHints.getDirectiveUIHints(dir);
    hints.add(h);
  }
  Collections.sort(hints,new Comparator<DirectiveUIHints>(){
    @Override public int compare(    DirectiveUIHints o1,    DirectiveUIHints o2){
      String l1=o1.getLabel();
      String l2=o2.getLabel();
      if (l1 == null && l2 != null)       return -1;
 else       if (l1 != null && l2 == null)       return 1;
 else       if (l1 == null && l2 == null)       return 0;
 else       return l1.compareTo(l2);
    }
  }
);
  ArrayList<DefaultMutableTreeNode> categoryNodes=new ArrayList<>();
  categoryNodes.add(other);
  for (  DirectiveUIHints h : hints) {
    DefaultMutableTreeNode parent=other;
    String category=h.getCategory();
    if (category != null && category.trim().length() > 0 && !category.trim().equalsIgnoreCase("String_Node_Str")) {
      category=category.trim();
      for (      DefaultMutableTreeNode n : categoryNodes) {
        String name=n.toString();
        if (name != null && name.equalsIgnoreCase(category)) {
          parent=n;
          break;
        }
      }
      if (parent == other) {
        parent=new DefaultMutableTreeNode(category);
        categoryNodes.add(parent);
      }
    }
    DefaultMutableTreeNode node=new DefaultMutableTreeNode(h);
    parent.add(node);
  }
  Collections.sort(categoryNodes,new Comparator<DefaultMutableTreeNode>(){
    @Override public int compare(    DefaultMutableTreeNode o1,    DefaultMutableTreeNode o2){
      return o1.toString().compareTo(o2.toString());
    }
  }
);
  for (  DefaultMutableTreeNode n : categoryNodes) {
    root.add(n);
  }
  treeModel.setRoot(root);
}

Fixed version (ground truth):
protected void populateDirectiveList(){
  DefaultTreeModel treeModel=(DefaultTreeModel)directivesTree.getModel();
  DefaultMutableTreeNode root=new DefaultMutableTreeNode("String_Node_Str");
  DefaultMutableTreeNode other=new DefaultMutableTreeNode("String_Node_Str");
  DirectiveManager directiveManager=DirectiveManager.getDirectiveManager();
  List<Class<? extends Directive>> directives=directiveManager.getDirectives();
  List<DirectiveUIHints> hints=new ArrayList<>();
  for (  Class<? extends Directive> dir : directives) {
    DirectiveUIHints h=DirectiveUIHints.getDirectiveUIHints(dir);
    hints.add(h);
  }
  Collections.sort(hints,new Comparator<DirectiveUIHints>(){
    @Override public int compare(    DirectiveUIHints o1,    DirectiveUIHints o2){
      String l1=o1.getLabel();
      String l2=o2.getLabel();
      if (l1 == null && l2 != null)       return -1;
 else       if (l1 != null && l2 == null)       return 1;
 else       if (l1 == null && l2 == null)       return 0;
 else       return l1.compareTo(l2);
    }
  }
);
  ArrayList<DefaultMutableTreeNode> categoryNodes=new ArrayList<>();
  categoryNodes.add(other);
  for (  DirectiveUIHints h : hints) {
    boolean added=false;
    String categoryAll=h.getCategory();
    if (categoryAll == null)     categoryAll="String_Node_Str";
    String[] categories=categoryAll.split("String_Node_Str");
    for (    String category : categories) {
      DefaultMutableTreeNode parent=null;
      if (category != null && category.trim().length() > 0) {
        category=category.trim();
        if (!category.equalsIgnoreCase("String_Node_Str")) {
          for (          DefaultMutableTreeNode n : categoryNodes) {
            String name=n.toString();
            if (name != null && name.equalsIgnoreCase(category)) {
              parent=n;
              break;
            }
          }
          if (parent == null) {
            parent=new DefaultMutableTreeNode(category);
            categoryNodes.add(parent);
          }
        }
      }
      if (parent != null) {
        DefaultMutableTreeNode node=new DefaultMutableTreeNode(h);
        parent.add(node);
        added=true;
      }
    }
    if (!added) {
      DefaultMutableTreeNode node=new DefaultMutableTreeNode(h);
      other.add(node);
    }
  }
  Collections.sort(categoryNodes,new Comparator<DefaultMutableTreeNode>(){
    @Override public int compare(    DefaultMutableTreeNode o1,    DefaultMutableTreeNode o2){
      return o1.toString().compareTo(o2.toString());
    }
  }
);
  for (  DefaultMutableTreeNode n : categoryNodes) {
    root.add(n);
  }
  treeModel.setRoot(root);
}