JTree File Browser solutions and a problem

Question

Hi everyone I have recently needed to create a file browser that allows addition, deletions and rename of files/directores using a JTree component.
I have searched the Sun web site and found a number of examples and from what I can see there are more or less two solutions. The first is to use the DefaultTreeModel and the DefaultMutableTreeNode classes and the other is to implement a new TreeModel taking advantage of a the File objects tree structure. This I found at;
http://java.sun.com/products/jfc/tsc/articles/jtree/
This to me seemed a very elegant solution. However it doesn't contain deletion, addition etc. So far I have tried to implement the addition of files but I have run into problems. The problem I have is that when I add a file a blank space ends up on the JTree view. If someone could take a look and suggest where I am going wrong I would be very greatful. The methods below I added to the FileSystemModel.java class from the url above.
     public File[] getPathToRoot(File file) {
     return getPathToRoot(file, 0);
    protected File[] getPathToRoot(File file, int i) {                              
     File[] files;
     if (file == null) {
         if (i == 0){
          return null;
         files = new File;
     } else {
     i++;
     if (file.equals( getRoot())){
               files = new File[i];
          }else{
          files = getPathToRoot(file.getParentFile(), i);
     files[files.length - i] = file;
     return files;
public void insertFileInto(String newFilePath, File parent) {
     File newFile = new File(parent, newFilePath);
     try{
          newFile.createNewFile();          
          } catch ( IOException io){
                         System.out.println("io ex");
     filesWereInserted( parent,newFile);
public void filesWereInserted(File file, File newFile) {          
     if (listenerList != null && file != null ) {
     Object[] objects = new Object[1];
          objects[0] = newFile;
          int [] is = new int[1];
          is[0] = 0;
     fireTreeNodesInserted(new TreeModelEvent(this, getPathToRoot(file), is, objects));
I basically looked at the DefaultTreeModel and tried to simluate the behaviour for files.
Since I have had this problem I remembered that out of the two solutions I have seen for a file browser the first is far more common. Perhaps I have chosse the wrong solution. Before I switch to the other soluion I thought I'ld put my problem to you guys and ask what you think the best solution is.
Thanks for any help :)

Answer 1

You are right this is a bad idea. You really want to implement delay loading. This means that your tree start out with only the top level folder expanded and dummy nodes in the folders that have children. Then using the expand events you can remove your dummy node and put in the real nodes before the tree displays the children. On the collapse event you can remove the real nodes and put back your dummy node (or you can leave the real nodes, that just means that eventually customers could have nodes for the entire system in memory, with a little work on their part:-). This way you only read the part of the file system that is visible and you only have the currently visible nodes in memory. I am sure you can find some examples of this technique.
While this could be done with the default models I feel that a custom model would be the way to go.
IL