Java Swing - 如何检查当前节点是否是JTree中的文件

import java.awt.Component;
import java.io.File;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;

public class Main {
  static DefaultMutableTreeNode createTreeModel(File file, boolean recursive) {
    DefaultMutableTreeNode node = new DefaultMutableTreeNode(file);
    if (file.isDirectory() && recursive) {
      File[] children = file.listFiles();
      if (children != null) {
        for (File f : children) {
          node.add(createTreeModel(f, recursive));
        }
      }
    }
    return node;
  }

  public static void main(String[] args) {
    JFrame frame = new JFrame(Main.class.getSimpleName());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    final JTree tree = new JTree(createTreeModel(
        new File(System.getProperty("user.dir")), true));
    tree.setCellRenderer(new DefaultTreeCellRenderer() {
      @Override
      public Component getTreeCellRendererComponent(JTree tree, Object value,
          boolean sel, boolean expanded, boolean leaf, int row, boolean hasFocus) {
        super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf,
            row, hasFocus);
        if (value instanceof DefaultMutableTreeNode) {
          DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;
          if (node.getUserObject() instanceof File) {
            setText(((File) node.getUserObject()).getName());
          }
        }
        return this;
      }
    });
    tree.getSelectionModel().addTreeSelectionListener(
        e -> {
          Object object = tree.getLastSelectedPathComponent();
          if (object instanceof DefaultMutableTreeNode) {
            Object userObject = ((DefaultMutableTreeNode) object)
                .getUserObject();
            if (userObject instanceof File) {
              File file = (File) userObject;
              System.out.println("Selected file" + file.getAbsolutePath()
                  + " Is directory? " + file.isDirectory());
            }
          }
        });
    JScrollPane pane = new JScrollPane(tree);
    frame.add(pane);
    frame.setSize(400, 600);
    frame.setVisible(true);
  }
}