scroll.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

import javax.swing.*;
import java.awt.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;

public class jtree extends JFrame {
	
    private JPanel panel;
    private JScrollPane scroll;
    private JTree tree;
    private DefaultMutableTreeNode root;
    private DefaultMutableTreeNode nodo1;
    private DefaultMutableTreeNode nodo2;
    private DefaultTreeModel model;
    
	public static void main(String args[]) {
	        new jtree().setVisible(true);
	}

    public jtree() {
        iniciarComponentes();
    }

    private void iniciarComponentes() {

        panel = new JPanel();
        scroll = new JScrollPane();  
        root = new DefaultMutableTreeNode("Raiz");
        nodo1 = new DefaultMutableTreeNode("nodo1");
        nodo2 = new DefaultMutableTreeNode("nodo2");
        model = new DefaultTreeModel(root);
        tree = new JTree(model);

        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setTitle("Prueba JTree");
        setResizable(false);
        getContentPane().setLayout(new FlowLayout());

        panel.setPreferredSize(new Dimension(200, 300));
        panel.setLayout(null);
        
        root.add(nodo1);
    	root.add(nodo2);

        scroll.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
        scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        scroll.setViewportView(tree);

        panel.add(scroll);
        scroll.setBounds(10, 10, 180, 280);

        getContentPane().add(panel);
        pack();
    } 
}