Multiple JTree is not appearing in JScrollPanel

Question

I am using the first example mentioned here for creating my JTree but I want to put more than one tree as root in the JscrollPanel. I just changed the layout of the box and create one more tree with the same code but when I run the program the tree is not appearing to me.

Here is my code

import java.awt.*;
import javax.swing.*;
import javax.swing.tree.*;

public class SimpleTree extends JFrame {
  public static void main(String[] args) {
    new SimpleTree();
  }

  public SimpleTree() {
    super("Creating a Simple JTree");
    Container content = getContentPane();
    Object[] hierarchy =
      { "javax.swing",
        "javax.swing.border",
        "javax.swing.colorchooser",
        "javax.swing.event",
        "javax.swing.filechooser",
        new Object[] { "javax.swing.plaf",
                       "javax.swing.plaf.basic",
                       "javax.swing.plaf.metal",
                       "javax.swing.plaf.multi" },
        "javax.swing.table",
        new Object[] { "javax.swing.text",
                       new Object[] { "javax.swing.text.html",
                                      "javax.swing.text.html.parser" },
                       "javax.swing.text.rtf" },
        "javax.swing.tree",
        "javax.swing.undo" };
    DefaultMutableTreeNode root = processHierarchy(hierarchy);
    DefaultMutableTreeNode root2 = processHierarchy(hierarchy);
    JTree tree = new JTree(root);
    JTree tree2 = new JTree(root2);
    content.setLayout(new BoxLayout(this,BoxLayout.Y_AXIS));
    content.add(new JScrollPane(tree));
    content.add(new JScrollPane(tree2));
    setSize(getPreferredSize());
    setVisible(true);
  }

  /** Small routine that will make node out of the first entry
   *  in the array, then make nodes out of subsequent entries
   *  and make them child nodes of the first one. The process is
   *  repeated recursively for entries that are arrays.
   */

  private DefaultMutableTreeNode processHierarchy(Object[] hierarchy) {
    DefaultMutableTreeNode node =
      new DefaultMutableTreeNode(hierarchy[0]);
    DefaultMutableTreeNode child;
    for(int i=1; i<hierarchy.length; i++) {
      Object nodeSpecifier = hierarchy[i];
      if (nodeSpecifier instanceof Object[])  // Ie node with children
        child = processHierarchy((Object[])nodeSpecifier);
      else
        child = new DefaultMutableTreeNode(nodeSpecifier); // Ie Leaf
      node.add(child);
    }
    return(node);
  }
}

Could someone please help me with this. All help would be really appreciated.

Thanks Ashish Tyagi

Answer 1

A JScrollPane has a view to a single child component in its ViewPort.

You could however place the 2 JScrollPane components on a single panel with say, an evenly split GridLayout(2, 1) and set the view of the JScrollPane to the new panel.

Aside: You should use the ContentPane as the container for BoxLayout:

content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));