This example shows how to expand or collapse all nodes of a JTree programmatically.

Example

Expand/Collapse JTree nodes

package com.logicbig.example;

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;
import java.util.ArrayList;
import java.util.Collections;

public class JTreeUtil {
  public static void setTreeExpandedState(JTree tree, boolean expanded) {
      DefaultMutableTreeNode node = (DefaultMutableTreeNode) tree.getModel().getRoot();
      setNodeExpandedState(tree, node, expanded);
  }

  public static void setNodeExpandedState(JTree tree, DefaultMutableTreeNode node, boolean expanded) {
      ArrayList<DefaultMutableTreeNode> list = Collections.list(node.children());
      for (DefaultMutableTreeNode treeNode : list) {
          setNodeExpandedState(tree, treeNode, expanded);
      }
      if (!expanded && node.isRoot()) {
          return;
      }
      TreePath path = new TreePath(node.getPath());
      if (expanded) {
          tree.expandPath(path);
      } else {
          tree.collapsePath(path);
      }
  }
}

Creating JTree

public class TreeExampleMain {
  public static void main(String[] args) {
      Hashtable<?, ?> projectHierarchyMap =
              TradingProjectDataService.instance.getProjectHierarchy();
      JTree tree = new JTree(projectHierarchyMap);
      JFrame frame = createFrame();
      frame.add(new JScrollPane(tree));
      frame.add(createTopPanel(tree), BorderLayout.NORTH);
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
  }

  private static JComponent createTopPanel(JTree tree) {
      JPanel panel = new JPanel();
      JButton expandBtn = new JButton("Expand All");
      expandBtn.addActionListener(ae-> {
          JTreeUtil.setTreeExpandedState(tree, true);
      });
      panel.add(expandBtn);
      JButton collapseBtn = new JButton("Collapse All");
      collapseBtn.addActionListener(ae-> {JTreeUtil.setTreeExpandedState(tree, false);});
      panel.add(collapseBtn);
      return panel;
  }

  private static JFrame createFrame() {
      JFrame frame = new JFrame("JTree Expand/Collapse example");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setSize(new Dimension(500, 400));
      return frame;
  }
}

Output

On clicking 'Expand All' button:

Example Project

Dependencies and Technologies Used:

• JDK 1.8
• Maven 3.3.9