import java.util.Enumeration;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeNode;
import javax.swing.tree.TreePath;

class TreeFrame implements TreeSelectionListener {
    private JTree example = null;
    public TreeFrame() {
        DefaultMutableTreeNode root = new DefaultMutableTreeNode(" root ", true);
        DefaultMutableTreeNode a = new DefaultMutableTreeNode(" A ");
        root.add(a);
        a.add(new DefaultMutableTreeNode(" AA "));
        a.add(new DefaultMutableTreeNode(" AB "));
        DefaultMutableTreeNode b = new DefaultMutableTreeNode(" B ");
        root.add(b);
        b.add(new DefaultMutableTreeNode(" BA "));
        b.add(new DefaultMutableTreeNode(" BB "));
        DefaultMutableTreeNode c = new DefaultMutableTreeNode(" C ");
        root.add(c);
        c.add(new DefaultMutableTreeNode(" AA "));
        c.add(new DefaultMutableTreeNode(" AB "));
        example = new JTree(root);
        example.addTreeSelectionListener(this);
        JPanel panel = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.X_AXIS));
        panel.add(new JScrollPane(example));
        JFrame frame = new JFrame(" JTreeDemo ");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(panel);
        frame.setSize(250, 400);
        frame.setVisible(true);
    }
    public void valueChanged(TreeSelectionEvent e) {
        example.expandPath(e.getPath());
        DefaultMutableTreeNode dm = (DefaultMutableTreeNode) e.getPath()
                .getLastPathComponent();
        for (Enumeration em = dm.children(); em.hasMoreElements();) {
            TreeNode n = (TreeNode) em.nextElement();
            TreePath visiblePath = new TreePath(((DefaultTreeModel) example
                    .getModel()).getPathToRoot(n));
            example.addSelectionPath(visiblePath);
        }
    }
}
public class TreeTest {
    public static void main(String[] args) {
        new TreeFrame();
    }
}

------解决方案--------------------

这样可以了。楼上意思可能理解错了
Java code

import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;

import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeNode;
import javax.swing.tree.TreePath;

class TreeFrame implements TreeSelectionListener {
  private JTree example = null;

  private List<TreeNode> allLeaf = new ArrayList<TreeNode>();

  public TreeFrame() {
    DefaultMutableTreeNode root = new DefaultMutableTreeNode(" root ", true);
    DefaultMutableTreeNode a = new DefaultMutableTreeNode(" A ");
    root.add(a);
    a.add(new DefaultMutableTreeNode(" AA "));
    a.add(new DefaultMutableTreeNode(" AB "));
    DefaultMutableTreeNode b = new DefaultMutableTreeNode(" B ");
    root.add(b);
    b.add(new DefaultMutableTreeNode(" BA "));
    b.add(new DefaultMutableTreeNode(" BB "));
    DefaultMutableTreeNode c = new DefaultMutableTreeNode(" C ");
    root.add(c);
    c.add(new DefaultMutableTreeNode(" AA "));
    c.add(new DefaultMutableTreeNode(" AB "));
    example = new JTree(root);
    example.addTreeSelectionListener(this);
    JPanel panel = new JPanel();
    panel.setLayout(new BoxLayout(panel, BoxLayout.X_AXIS));
    panel.add(new JScrollPane(example));
    JFrame frame = new JFrame(" JTreeDemo ");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setContentPane(panel);
    frame.setSize(250, 400);
    frame.setVisible(true);
    
    visitAllNodes(example);
  }

  public void valueChanged(TreeSelectionEvent e) {
    example.expandPath(e.getPath());
    DefaultMutableTreeNode dm =
        (DefaultMutableTreeNode) e.getPath().getLastPathComponent();
    DefaultMutableTreeNode root =
        (DefaultMutableTreeNode) example.getModel().getRoot();
    for (TreeNode leaf : allLeaf) {
      if (leaf.toString().equals(dm.toString())) {
        TreePath visiblePath =
            new TreePath(((DefaultTreeModel) example.getModel())
                .getPathToRoot(leaf));
        example.addSelectionPath(visiblePath);
      }
    }
  }

  public void visitAllNodes(JTree tree) {
    DefaultMutableTreeNode root = (DefaultMutableTreeNode) tree.getModel().getRoot();
    Enumeration breadthFirst = root.breadthFirstEnumeration();
    while (breadthFirst.hasMoreElements()) {
      TreeNode node = (TreeNode) breadthFirst.nextElement();
      if (node.isLeaf()) {
        allLeaf.add(node);
      }
    }
  }
}

public class TreeTest {
  public static void main(String[] args) {
    new TreeFrame();
  }
}