JFrame frame1 = new JFrame("Title 1");
JFrame frame2 = new JFrame("Title 2");
.....

If frame2 is created in a different part of your program, pass the reference
either through the method call parameters, or instance variables (if the
frames are created within different methods of the same class), or
properties, etc.

Note that there is no such thing as a "parent" frame. Each JFrame is created
separately, and has life of its own. There is an "owner" window
(JFrame/Frame/JDialog/Dialog) that can be associated with a Dialog (or
JDialog), but there is no owner for a Frame/JFrame.

(Alex)

That is not necessary.

This may help give you a start.

<sscce>
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/** Uses the Frame.getFrames() method to find other Frames and
JFrames and bring them 'toFront'.  See getOwnedWindows()for
windows and dialogs. */
public class UpFront extends
 Frame implements ActionListener {

 static int number = 0;

 static final String NAME = "UpFront ";

 public UpFront() {
   super( NAME + number);
   setLayout( new GridLayout(0,1) );

   // assemble the UI
   Button b = new Button("All");
   b.addActionListener(this);

   // add a button for each known frame
   Frame[] allFrame = Frame.getFrames();
   add(b);
   for( int ii=0; ii<allFrame.length; ii++ ) {
     b = new Button( NAME + ii );
     b.addActionListener(this);
     add(b);
   }

   pack();
   setLocation( (getWidth()-5)*number++, 10 );
 }

 public void actionPerformed(ActionEvent ae) {
   String command = ae.getActionCommand();

   // a very handy static method of Frame
   Frame[] allFrame = Frame.getFrames();
   for( int ii=0; ii<allFrame.length; ii++ ) {
     String title = allFrame[ii].getTitle();
     if ( command.equals("All") ) {
       // bring all frames to front in turn
       allFrame[ii].toFront();
       System.out.println( title + ".toFront()" );
     } else {
       if ( command.equals( title ) ) {
         // bring only the named frame to front
         allFrame[ii].toFront();
         System.out.println( title + ".toFront()" );
       }
     }
   }
 }

 /** Accepts no arguments. */
 public static void main(String[] args) {
   for ( int ii=0; ii<5; ii++ ) {
     new UpFront().setVisible(true);
   }
   JFrame f = new JFrame("JFrame");
   f.getContentPane().add(
     new JLabel("This is a JFrame, rather than an 'UpFront'") );
   f.pack();
   f.setVisible(true);
 }
}
</sscce>

HTH