Implementando el MessageBox java

public class SWT{public static void main(String[]args){
final org.eclipse.swt.widgets.Display display =
		new org.eclipse.swt.widgets.Display();
final org.eclipse.swt.widgets.Shell shell = new org.eclipse.swt.widgets.Shell(display);shell.setLayout(
	new org.eclipse.swt.layout.FillLayout());
org.eclipse.swt.widgets.MessageBox messageBox = new org.eclipse.swt.widgets.MessageBox(
		shell,org.eclipse.swt.SWT.OK);
	messageBox.setMessage(" Hola Mundo");
	shell.pack();
	shell.setSize(630,300);
	messageBox.open();
	shell.open();
while (!shell.isDisposed()) {
    if (!display.readAndDispatch())
       display.sleep();
 }
 display.dispose();  
	}