import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class TestShells {
    public static void main(String[] args) {
        Display display = new Display();
        boolean condition1=false;
        boolean condition2=false;

        if(condition1) {
            new Shell1();
            eventLoop(display);
        }

        if(condition2) {
            new Shell2();
            eventLoop(display);
        }

        new Shell3();
        eventLoop(display);

        display.dispose();
    }

    /**
     * @param display
     */
     private static void eventLoop(Display display) {
         while (display.getShells().length > 0) {
             if (!display.readAndDispatch()) {
                 display.sleep();
             }
         }
     }
}

class Shell1 {
    Shell1() {
        Display display = Display.getDefault();
        Shell shell = new Shell(display);
        shell.setText("Shell 1");
        shell.open();
    }
}

class Shell2 {
    Shell2() {
        Display display = Display.getDefault();
        Shell shell = new Shell(display);
        shell.setText("Shell 2");
        shell.open();
    }
}

class Shell3 {
    Shell3() {
        Display display = Display.getDefault();
        Shell shell = new Shell(display);
        shell.setText("Shell 3");
        shell.open();
    }
}