Mine

package test;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class Test2 {
	static boolean c1True = true;
public static void main(String[] args) {
	Display display = new Display();
	Shell shell = new Shell(display);
	shell.setLayout(new GridLayout(1, false));

	Composite parent = new Composite(shell, SWT.NONE);
//	parent.setLayout(new FillLayout());
	
	final Composite c1 = new Composite(parent, SWT.NONE);
	c1.setBackground(display.getSystemColor(SWT.COLOR_RED));
	c1.setBounds(0, 0, 500, 500);
	final Composite c2 = new Composite(parent, SWT.NONE);
	c2.setBackground(display.getSystemColor(SWT.COLOR_GREEN));
	c2.setBounds(0, 0, 500, 500);
	
	Button b = new Button(shell, SWT.PUSH);
	b.addSelectionListener(new SelectionListener() {
		
		@Override
		public void widgetSelected(SelectionEvent e) {
		 if (c1True) {
			 c2.moveAbove(c1);
		 } else {
			 c1.moveAbove(c2);
		 }
			c1True = !c1True;
		}
		
		@Override
		public void widgetDefaultSelected(SelectionEvent e) {
			// TODO Auto-generated method stub
			
		}
	});
	shell.pack();
	shell.open();
	while (!shell.isDisposed()) {
		if (!display.readAndDispatch())
			display.sleep();
	}
	display.dispose();
}
}