JTree, TreeNode (DefaultMutableTreeNode), And TreePath Classes

JTree class is a handy tool to manipulate tree structured data. It takes care of how the data is presented graphically, and does all the editing, adding and deleting of the tree nodes. I would like to put a few notes, or precautions, for JTree and all related classes, which would makes it more valuable to Java programmers -- since all JTree, TreeNode (DefaultMutableTreeNode), and TreePath classes are involved, and the documentations might not be there for -- those who need them.

First of all, you must have this in mind -- JTree takes care of how the tree is presented whereas DefaultMutableTreeNode does all the structual data manipulation such as adding or deleting a TreeNode. My point here is this -- there are JTree and DefaultMutableTreeNode and JTree is not equipped with method that can access to a TreeNode object. JTree must access to TreeNode via TreePath. The following code shows the process, to collapse a tree node.

 TreeNode list[]=node.getPath();
 TreePath path=new TreePath(list);
 tree.collapsePath(path);

The TreePath can point to a TreeNode, and PathComponent and TreeNode is used in method names interchangeably, so this can be confusing. This line shows how to get the selected TreeNode of a JTree.

 DefaultMutableTreeNode selectedNode=
     (DefaultMutableTreeNode) tree.getLastSelectedPathComponent();

Lastly, this will collapse all the TreeNode in a JTree.

    void collapseNode(DefaultMutableTreeNode n)
    {
 for (Enumeration e=n.postorderEnumeration(); e.hasMoreElements() ; )
     {
  DefaultMutableTreeNode node=(DefaultMutableTreeNode)e.nextElement();
  TreeNode list[]=node.getPath();
  TreePath path=new TreePath(list);
  if(!node.isRoot())
      {
   tree.collapsePath(path);
      }
     } 
    }