Preventing a JInternalFrame from being moved

You can subclass the protected class BorderListener that is defined in BasicInternalFrameUI and provide an empty implementation for mouseDragged. In the following example, it is done so for the Metal look and feel.

Main.java:

import javax.swing.plaf.basic.*;
import javax.swing.plaf.metal.*;
import javax.swing.event.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.*;
import java.net.*;
 
public class Main extends JFrame {
   JDesktopPane desktop;
   int nframes = 0;
 
   JMenu internalFrameMenu;
 
   public Main() {
      desktop = new JDesktopPane(); 
      setContentPane(desktop);
      setJMenuBar(createMenuBar());
      createInternalFrame(); 
   }
 
   protected JMenuBar createMenuBar() {
      JMenuBar menuBar = new JMenuBar();
 
      JMenu createMenu = new JMenu("Create");
      createMenu.setMnemonic(KeyEvent.VK_C);
      JMenuItem newMenuItem = new JMenuItem("New");
      newMenuItem.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            createInternalFrame();
         }
      }); 
      newMenuItem.setMnemonic(KeyEvent.VK_N);
      createMenu.add(newMenuItem);
      menuBar.add(createMenu);
  
      return menuBar;
   }
 
   protected void createInternalFrame() {
      nframes++;
      String title = "JInternalFrame #" + nframes;
      JInternalFrame frame = new JInternalFrame(title,
         true,    // resizable
         true,    // closable
         true,    // maximizable
         true);   // iconifiable
      frame.setVisible(true); 
      desktop.add(frame);
      frame.setSize(200, 200);
      frame.setLocation(30*nframes, 30*nframes);
      try {
         frame.setSelected(true);
      } catch (java.beans.PropertyVetoException e) {}
 
      frame.setUI(new MyMetalInternalFrameUI(frame));
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setSize(500, 300);
      main.setVisible(true);
   }
}
 
class MyMetalInternalFrameUI extends MetalInternalFrameUI {
   public MyMetalInternalFrameUI(JInternalFrame b) { super(b); }
 
   protected MouseInputAdapter createBorderListener(JInternalFrame w) {
      return new MyBorderListener();
   }
 
   protected class MyBorderListener extends BasicInternalFrameUI.BorderListener {
      public void mouseDragged(MouseEvent e) {  }
   }
}