TreeNode ClassCastException?

[Max Power]

hello, whats wrong with this code:

 
 
    public TreePath findByName(JTree tree, String[] names) {
        
        //ClassCastException in this line???
        TreeNode root = (TreeNode)tree.getModel().getRoot();
        return find2(tree, new TreePath(root), names, 0, true);
    }
 

why that? this code is from a book so i think it is correct.

THANKS

[Stefan Krompass]

Hi,

the method getRoot() of interface javax.swing.tree.TreeModel returns an instance of class java.lang.Object. So the object returned is not necessarily an instance of class javax.swing.tree.TreeNode. Can you please post a working sample where we can reproduce your problem?

Stefan

[Max Power]

hi, here it is. this code displays the filesystem inside a jtree. just start it with some existing path like c:\. after 3 seconds a method is called and the exception occurs.....

import javax.swing.*;
import javax.swing.tree.TreeModel;
import javax.swing.tree.TreePath;
import javax.swing.event.TreeModelListener;
import javax.swing.event.TreeModelEvent;
import javax.swing.event.EventListenerList;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.util.*;
import java.util.HashMap;
import java.io.File;
import java.io.Serializable;
import javax.swing.tree.*;
 

public class FileTreeModel implements TreeModel, Serializable, Cloneable {
protected EventListenerList listeners;
 
private Map map;
 
private File root;
 
public FileTreeModel(File root) {
if (!root.exists())
throw new IllegalArgumentException(String.valueOf(root));
 
this.root = root;
 
this.listeners = new EventListenerList();
 
this.map = new HashMap();
}
 
public Object getRoot() {
return root;
}
 
public boolean isLeaf(Object node) {
return !((File) node).isDirectory();
}
 
public int getChildCount(Object node) {
List children = children(node);
 
if (children == null)
return 0;
 
return children.size();
}
 
public Object getChild(Object parent, int index) {
return children(parent).get(index);
}
 
public int getIndexOfChild(Object parent, Object child) {
return children(parent).indexOf(child);
}
 
public void valueForPathChanged(TreePath path, Object value) {
}
 
protected List children(Object node) {
File f = (File) node;
 
if (!f.isDirectory())
return null;
 
List children = (List) map.get(f);
 
if (children == null) {
File[] c = f.listFiles();
 
if (c == null)
return null;
 
children = new ArrayList(c.length);
 
for (int len = c.length, i = 0; i < len; i++)
children.add(c[i]);
 
map.put(f, children);
}
 
return children;
}
 
public Object clone() {
try {
FileTreeModel clone = (FileTreeModel) super.clone();
 
clone.listeners = new EventListenerList();
 
return clone;
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
}
 
public void addTreeModelListener(TreeModelListener l) {
listeners.add(TreeModelListener.class, l);
}
 
public void removeTreeModelListener(TreeModelListener l) {
listeners.remove(TreeModelListener.class, l);
}

//-----------------
// Finds the path in tree as specified by the node array.
    // The node array is a sequence of nodes where nodes[0]
    // is the root and nodes[i] is a child of nodes[i-1].
    // Comparison is done using Object.equals().
    // Returns null if not found.
    public TreePath find(JTree tree, Object[] nodes) {
        TreeNode root = (TreeNode)tree.getModel().getRoot();
        return find2(tree, new TreePath(root), nodes, 0, false);
    }
    
    // Finds the path in tree as specified by the array of names.
    // The names array is a sequence of names where names[0]
    // is the root and names[i] is a child of names[i-1].
    // Comparison is done using String.equals().
    // Returns null if not found.
    public static TreePath findByName(JTree tree, String[] names) {
        TreeNode root = (TreeNode)tree.getModel().getRoot();
        return find2(tree, new TreePath(root), names, 0, true);
    }
    private static TreePath find2(JTree tree, TreePath parent, Object[] nodes, int depth, boolean byName) {
        TreeNode node = (TreeNode)parent.getLastPathComponent();
        Object o = node;
    
        // If by name, convert node to a string
        if (byName) {
            o = o.toString();
        }
    
        // If equal, go down the branch
        if (o.equals(nodes[depth])) {
            // If at end, return match
            if (depth == nodes.length-1) {
                return parent;
            }
    
            // Traverse children
            if (node.getChildCount() >= 0) {
                for (Enumeration e=node.children(); e.hasMoreElements(); ) {
                    TreeNode n = (TreeNode)e.nextElement();
                    TreePath path = parent.pathByAddingChild(n);
                    TreePath result = find2(tree, path, nodes, depth+1, byName);
                    // Found a match
                    if (result != null) {
                        return result;
                    }
                }
            }
        }
    
        // No match at this branch
        return null;
    }
 

//-----------------
 

 
public static void main(String[] args) {
if (args.length != 1) {
System.err.println("Usage: java FileTreeModel path");
System.exit(1);
}
 
File root = new File(args[0]);
 
if (!root.exists()) {
System.err.println(root + ": No such file or directory");
System.exit(2);
}
 
JTree t = new JTree(new FileTreeModel(root));
 
//t.setCellRenderer(new Renderer());
JFrame f = new JFrame(root.toString());
 
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
f.getContentPane().add(new JScrollPane(t));
 
f.pack();
f.setVisible(true);
try{
Thread.sleep(3000);
}catch(Exception te){
}

System.out.println("Now comes the error....");
TreePath path = findByName(t, new String[]{"JTree", "food", "bananas"});


}
}

i can send you this code as well....?

THANKS IN ADVANCE :-)

[Stefan Krompass]

Originally posted by Andreas Golchert:

...
private File root;
 
public FileTreeModel(File root) {
  this.root = root;
  ...
}
 
public Object getRoot() {
  return root;
}
...

This is the solution: Your getRoot()-method returns an instance of class File...

Stefan

[Max Power]

hi, do you know how to change this?

thanks:-)

[Stefan Krompass]

Hi,

what you have to do is distinguish between the types of nodes you click on... (leaf -> file, non-leaf -> directory). You could try using DefaultMutableTreeNode as a "wrapper" around your file-object. Just as a few suggestions...

Stefan

[Max Power]

hi, thanks. can you go a bit more into detail?

i am still stuck...

[Stefan Krompass]

Hi,

my solution yould look something like this. What I did, is to wrap the File-objects in DefaultMutableTreeNodes. We have to do this to separate the model (the File-objects) from the view (the nodes of the JTree).

import javax.swing.*;
import javax.swing.tree.TreeModel;
import javax.swing.tree.TreePath;
import javax.swing.event.TreeModelListener;
import javax.swing.event.TreeModelEvent;
import javax.swing.event.EventListenerList;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.util.*;
import java.util.HashMap;
import java.io.File;
import java.io.Serializable;
import javax.swing.tree.*;
 
 
public class FileTreeModel implements TreeModel, Serializable, Cloneable {
  protected EventListenerList listeners;
  private Map map;
  private File file;
  private DefaultMutableTreeNode root;
  
  public FileTreeModel(DefaultMutableTreeNode root) {
    File f = (File) root.getUserObject();
    if (!f.exists())
      throw new IllegalArgumentException(String.valueOf(root));
      this.file = f;
      this.root = root;
      this.listeners = new EventListenerList();
      this.map = new HashMap();
  }
 
  public Object getRoot() {
    return root;
  }
 
  public boolean isLeaf(Object node) {
    DefaultMutableTreeNode n = (DefaultMutableTreeNode) node;
    File f = (File) n.getUserObject();
    return !f.isDirectory();
  }
 
  public int getChildCount(Object node) {
    List children = children(node);
    if (children == null)
      return 0;
    return children.size();
  }
 
  public Object getChild(Object parent, int index) {
    return children(parent).get(index);
  }
 
  public int getIndexOfChild(Object parent, Object child) {
    return children(parent).indexOf(child);
  }
 
  public void valueForPathChanged(TreePath path, Object value) {
  }
 
  protected List children(Object node) {
    DefaultMutableTreeNode n = (DefaultMutableTreeNode) node;
    File f = (File) n.getUserObject();
    if (!f.isDirectory())
      return null;
 
    List children = (List) map.get(f);
 
    if (children == null) {
      File[] c = f.listFiles();
      if (c == null)
        return null;
      children = new ArrayList(c.length);
      for (int len = c.length, i = 0; i < len; i++)
        children.add(new DefaultMutableTreeNode(c[i]));
      map.put(f, children);
    }
    return children;
  }
 
  public Object clone() {
    try {
      FileTreeModel clone = (FileTreeModel) super.clone();
      clone.listeners = new EventListenerList();
      return clone;
    } catch (CloneNotSupportedException e) {
      throw new InternalError();
    }
  }
 
  public void addTreeModelListener(TreeModelListener l) {
    listeners.add(TreeModelListener.class, l);
  }
 
  public void removeTreeModelListener(TreeModelListener l) {
    listeners.remove(TreeModelListener.class, l);
  }

  //-----------------
  // Finds the path in tree as specified by the node array.
  // The node array is a sequence of nodes where nodes[0]
  // is the root and nodes[i] is a child of nodes[i-1].
  // Comparison is done using Object.equals().
  // Returns null if not found.
  public TreePath find(JTree tree, Object[] nodes) {
    TreeNode root = (TreeNode)tree.getModel().getRoot();
    return find2(tree, new TreePath(root), nodes, 0, false);
  }
    
  // Finds the path in tree as specified by the array of names.
  // The names array is a sequence of names where names[0]
  // is the root and names[i] is a child of names[i-1].
  // Comparison is done using String.equals().
  // Returns null if not found.
  public static TreePath findByName(JTree tree, String[] names) {
    TreeNode root = (TreeNode)tree.getModel().getRoot();
    return find2(tree, new TreePath(root), names, 0, true);
  }
  private static TreePath find2(JTree tree, TreePath parent,
        Object[] nodes, int depth, boolean byName) {
    TreeNode node = (TreeNode)parent.getLastPathComponent();
    Object o = node;
    // If by name, convert node to a string
    if (byName) {
      o = o.toString();
    }
    // If equal, go down the branch
    if (o.equals(nodes[depth])) {
      // If at end, return match
      if (depth == nodes.length-1) {
        return parent;
      }
    
      // Traverse children
      if (node.getChildCount() >= 0) {
        for (Enumeration e=node.children(); e.hasMoreElements(); ) {
          TreeNode n = (TreeNode)e.nextElement();
          TreePath path = parent.pathByAddingChild(n);
          TreePath result = find2(tree, path, nodes, depth+1, byName);
          // Found a match
          if (result != null) {
            return result;
          }
        }
      }
    } 
    // No match at this branch
    return null;
  }
  
  public static void main(String[] args) {
    if (args.length != 1) {
      System.err.println("Usage: java FileTreeModel path");
      System.exit(1);
    }
 
    File root = new File(args[0]);
 
    if (!root.exists()) {
      System.err.println(root + ": No such file or directory");
      System.exit(2);
    }
 
    DefaultMutableTreeNode r = new DefaultMutableTreeNode(root);
    JTree t = new JTree(new FileTreeModel(r));
    //t.setCellRenderer(new Renderer());
    JFrame f = new JFrame(root.toString());
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.getContentPane().add(new JScrollPane(t));
    f.pack();
    f.setVisible(true);
    try{
      Thread.sleep(3000);
    }catch(Exception te){
    }

    System.out.println("Now comes the error....");
      TreePath path = findByName(t, new String[]{"JTree", "food", "bananas"});
  }
}

Stefan