密码框组件

public class asd extends JFrame{

    public asd() {
        // TODO Auto-generated constructor stub
    Container c = getContentPane();
    setVisible(true);
    setSize(300,200);
    setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    JPasswordField jp = new JPasswordField();
    c.add(jp);
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        new asd();
    }

}