下列程序构造了一个 Swing Applet ，请在下划线处填入正确的代码

Import javax.swing.*;

Import java.awt.*;

Public class SwingApplet extends ( 13 ) {

Jlabel l = new Jlabel ( “ This is a Swing Applet. ” );

Public void init(){

C．ontainer contentPane = getContentPane();

contentPane.add(1);

}

}