SWT で窓を出すだけのそれ。

WindowSample1.java

import org.eclipse.swt.widgets.*;


public class WindowSample1 {
    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell( display );

        shell.setText( "Window Sample1" );
        shell.setSize( 300, 200 );
        shell.open();

        while ( !shell.isDisposed() ) {
            if ( !display.readAndDispatch() ) {
                display.sleep();
            }
        }
        display.dispose();
    }
}