Question

I have a list populated with duplicate entries. I am using a hash to store each unique entry from this list. Each key will then point to an object of type DefaultMutableTreeNode which represents the JTree node. My goal is to have this node point to all entries from the list which have the same node-same as the parent.

I have added these parent-nodes without problems but when the children nodes are added (via insertNodeInto), only parent nodes appear. A code-snippet is below; am very appreciative for advice / time.

// an unsorted list of items
List<MyObject>list = hash.get(key);

// clause to check for size
if (list.size() > 0) {

    // iterate through each item in the list and fetch obj
    for (int i=0; i < list.size(); i++) {
        MyObject be = list.get(i);

        // if object is not in hash, add to hash and point obj to new node
        if (!hashParents.containsKey(be)) {
                DefaultMutableTreeNode parent = 
                    new DefaultMutableTreeNode(be.getSequence());

                // add the key and jtree node to hash
                hashParents.put(be, parent);    

                // insert node to tree, relead model        
                ((DefaultMutableTreeNode)(root)).insert(
                    new DefaultMutableTreeNode("parent node"), 
                    root.getChildCount());
                    ((DefaultTreeModel)(tree.getModel())).reload();
        }

        // now that a parent-node exists, create a child 
        DefaultMutableTreeNode child = new DefaultMutableTreeNode("child");

        // insert the new child to the parent (from the hash)
        ((DefaultTreeModel)(tree.getModel())).insertNodeInto(child, hashParents.get(be), 
            hashParents.get(be).getChildCount());

        // render the tree visible          
        ((DefaultTreeModel)(tree.getModel())).reload();
    }
}

Answer 1

You make mistake here

// insert node to tree, relead model        
((DefaultMutableTreeNode)(root)).insert(
   new DefaultMutableTreeNode("parent node"), 
   root.getChildCount());

You already create node parent above, but don’t use it. You insert in tree another node, but child nodes you still insert in parent. That’s why they don’t appear in tree.

This code fragment look like

// insert node to tree, relead model        
((DefaultMutableTreeNode)(root)).insert(
   parent, 
   root.getChildCount());