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import java.awt.BorderLayout;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeExpansionEvent;
import javax.swing.event.TreeWillExpandListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.ExpandVetoException;
import javax.swing.tree.TreePath;
public class TreeWillExpandListenerDemo {
public static void main(String args[]) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
root.add(new DefaultMutableTreeNode("A"));
root.add(new DefaultMutableTreeNode("B"));
root.add(new DefaultMutableTreeNode("C"));
JTree tree = new JTree(root);
TreeWillExpandListener treeWillExpandListener = new TreeWillExpandListener() {
public void treeWillCollapse(TreeExpansionEvent treeExpansionEvent)
throws ExpandVetoException {
TreePath path = treeExpansionEvent.getPath();
DefaultMutableTreeNode node = (DefaultMutableTreeNode) path.getLastPathComponent();
String data = node.getUserObject().toString();
System.out.println("WillCollapse: " + data);
}
public void treeWillExpand(TreeExpansionEvent treeExpansionEvent) throws ExpandVetoException {
TreePath path = treeExpansionEvent.getPath();
DefaultMutableTreeNode node = (DefaultMutableTreeNode) path.getLastPathComponent();
String data = node.getUserObject().toString();
System.out.println("WillExpand: " + data);
}
};
tree.addTreeWillExpandListener(treeWillExpandListener);
JScrollPane scrollPane = new JScrollPane(tree);
frame.add(scrollPane, BorderLayout.CENTER);
frame.setSize(300, 150);
frame.setVisible(true);
}
}
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