Java tutorial
//package com.java2s; import java.util.Enumeration; import javax.swing.JTree; import javax.swing.tree.DefaultMutableTreeNode; import javax.swing.tree.TreePath; public class Main { public static void expandTree(JTree tree) { DefaultMutableTreeNode root = (DefaultMutableTreeNode) tree.getModel().getRoot(); @SuppressWarnings("unchecked") Enumeration<DefaultMutableTreeNode> e = root.breadthFirstEnumeration(); while (e.hasMoreElements()) { DefaultMutableTreeNode node = (DefaultMutableTreeNode) e.nextElement(); if (node.isLeaf()) continue; int row = tree.getRowForPath(new TreePath(node.getPath())); tree.expandRow(row); } } }