关于Java的事件监听，问题出在哪？

Question

代码如下，提示"cannot be resolved to type"（已在注释中标出），但我认为没有问题啊

 package QAppLet;
import java.awt.*;
import java.awt.event.*;
import java.awt.Button;
public class Complete {
    public static void main(String[] args) {
        MyFrame m=new MyFrame("字符比较器");
    }

}
class MyFrame extends Frame{
    MyFrame(String s){
        super(s);
        setVisible(true);
        setLayout(new FlowLayout());
        TextField f1=new TextField(50);
        TextField f2=new TextField(50);
        TextField f3=new TextField(10);
        Label la1=new Label();
        Label la2=new Label();
        Label la3=new Label();
        la1.setText("y原始值");
        la2.setText("比较值");
        la3.setText("比较结果");
        Button b=new Button("确定");
        this.addWindowListener(new WindowAdapter(){
            public void windowClosing(WindowEvent e){
                setVisible(false);
                System.exit(0);
            }
        });
        add(la1);
        add(f1);
        add(la2);
        add(f2);
        add(la3);
        f3.setEditable(false);
        add(f3);
        add(b);
        b.addActionListener(new Act());   //提示“Act cannot be resolved to type"
        class Act implements ActionListener{
            public void actionPerformed(ActionEvent e){
                if((f1.getText()).equals(f2.getText()))
                    f3.setText("相等");
                else
                    f3.setText("不相等");
            }
        }

    }
}

Answer 1