import javax.swing.JFrame;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;

public class JtreeProba extends JFrame {

    JTree tree = new JTree();
    DefaultMutableTreeNode root = new DefaultMutableTreeNode("root");
    DefaultMutableTreeNode egy = new DefaultMutableTreeNode("egy");
    DefaultMutableTreeNode ketto = new DefaultMutableTreeNode("kettő");
    DefaultTreeModel model = new DefaultTreeModel(root);    
    
    public JtreeProba() {
        model.insertNodeInto(egy, root, 0);
        model.insertNodeInto(ketto, root, 0);
        
        this.tree.setModel(model);
        
        this.add(tree);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(300, 200);
        this.setVisible(true);
    }
    
    public static void main(String[] args) {
        new JtreeProba();
    }    
}