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JTree DynamicUtilTreeNode Class

The JTree class has an inner class, JTree.DynamicUtilTreeNode The JTree uses it to create the nodes for your trees. The DynamicUtilTreeNode is a DefaultMutableTreeNode subclass The DynamicUtilTreeNode doesn't create its child nodes until they're needed. The child nodes are needed when you either expand the parent node or try to traverse a tree. import java.awt.BorderLayout; import java.util.Hashtable; import javax.swing.JFrame; import javax.swing.JScrollPane; import javax.swing.JTree; import javax.swing.tree.DefaultMutableTreeNode; public class DynamicUtilTreeNodeDemo {   public static void main(String args[]) {     JFrame frame = new JFrame();     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);     DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");     Hashtable<String, Object> hashtable = new Hashtable<String, Object>();     hashtable.put ("Two", new String[]{"A", "B", "C"});          Hashtable<Object, Object> innerHashtable = new Hashtable<Object, Object>();     innerHashtable.put ("Two", new String[]{"A", "B", "C"});          hashtable.put ("Three", innerHashtable);     JTree.DynamicUtilTreeNode.createChildren(root, hashtable);     JTree tree = new JTree(root);          JScrollPane scrollPane = new JScrollPane(tree);     frame.add(scrollPane, BorderLayout.CENTER);     frame.setSize(300, 150);     frame.setVisible(true);   } }