Using JTree

JTree is a tree component in swing technology, JTree usually used to representation of tree hierarchy like folder on Windows Explorer. This tutorial is show you howto showing folder hierarchy using JTree component.
1. Create a new project or open your exam project
2. Create a new JFrame class, in this case i called JTreeFolder
3. Drag, Drop and design form like this:

and this in Inspector:

4. Open "Source" tab and goto constructor:

public JTreeFolder() {
    initComponents();      
}

under:

initComponents();

write this code:

File dir = new File("C:/windows");
DefaultMutableTreeNode root = new DefaultMutableTreeNode(dir);
scan(dir, root);
tree.setModel(new DefaultTreeModel(root));

5. We need to create one method to scan folder, this method is run recursively:

private void scan(File file, DefaultMutableTreeNode root) {
    for (File f : file.listFiles()) {
        DefaultMutableTreeNode node = new DefaultMutableTreeNode(f.getName());
        root.add(node);
        if (f.isDirectory()) {
            scan(f, node);
        }
    }
}

6. Finally run the project and we get this:


Conclusion:
To representation node in JTree simple way is using DefaultMutableTreeNode.
Complete Sourcecode:

/*
 * JTreeFolder.java
 *
 * Created on 16 Juli 2008, 22:07
 */
package org.kazao.tips.tip006;

import java.io.File;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;

/**
 *
 * @author  Mr. Kazao
 */
public class JTreeFolder extends javax.swing.JFrame {

    /** Creates new form JTreeFolder */
    public JTreeFolder() {
        initComponents();
        File dir = new File("C:/windows");
        DefaultMutableTreeNode root = new DefaultMutableTreeNode(dir);
        scan(dir, root);
        tree.setModel(new DefaultTreeModel(root));
    }

    private void scan(File file, DefaultMutableTreeNode root) {
        for (File f : file.listFiles()) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(f.getName());
            root.add(node);
            if (f.isDirectory()) {
                scan(f, node);
            }
        }
    }

    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // //GEN-BEGIN:initComponents
    private void initComponents() {

        scroller = new javax.swing.JScrollPane();
        tree = new javax.swing.JTree();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Using JTree to scaning folder");

        scroller.setName("scroller"); // NOI18N

        tree.setName("tree"); // NOI18N
        scroller.setViewportView(tree);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(scroller, javax.swing.GroupLayout.DEFAULT_SIZE, 380, Short.MAX_VALUE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(scroller, javax.swing.GroupLayout.DEFAULT_SIZE, 278, Short.MAX_VALUE)
                .addContainerGap())
        );

        pack();
    }// //GEN-END:initComponents

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new JTreeFolder().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify//GEN-BEGIN:variables
    public javax.swing.JScrollPane scroller;
    public javax.swing.JTree tree;
    // End of variables declaration//GEN-END:variables
}