填空题 下面是生成一个依赖窗口的对话框，属性为modal，请把所缺的代码补齐。 import java.awt.*; public class DialogDemo extends Frame { DialogDemo() { SetTitle("Demo"); Panel p=new Panel(); p.add(new label("one")); p.add(new Checkbox ("two")); add("North",p); add("Center",new TextArea("three",3,10)); Dialog d=new Dialog(this," a cat",{{U}} 【12】 {{/U}}); d.add("North",new Label ("Modal dialog"); d.add("Center",new TextArea("hello"); d.pack (); d.show (); } public static void main(String args[]) { DialogDemo f=new DialogDemo(); f.pack(); f.show(); } }