sclass FrameCoActivator {
  long lastTime;
  int timeout = 100; // prohibit endless loop
  
  *(JFrame f1, final JFrame f2) {
    link(f1, f2, "zoom");
    link(f2, f1, "boom.");
  }
  
  void link(final JFrame f1, final JFrame f2, fS text) {
    f1.addWindowListener(new WindowAdapter {
      public void windowIconified(WindowEvent e) {
        lastTime = sysNow();
      }
      
      public void windowActivated(WindowEvent e) {
        if (sysNow() >= lastTime+timeout) {
          lastTime = sysNow();
          //print(text);
          activateFrame(f2);
          activateFrame(f1);
        }
      }
    });
  }
}

svoid coActivateFrames(JFrame f1, final JFrame f2) {
  new FrameCoActivator(f1, f2);
}