Java 按钮事件处理程序无法解析

Java button event handler won't resolve

我正在尝试在我的 GUI 上设置偶数处理程序。但是,当我声明 class 然后在按钮上调用它时,它无法解析?

btnHigher = new JButton("Higher");
    btnHigher.setBounds(190, 110, 75, 50);
    btnHigher.addActionListener(new HigherHandler());
    panel.add(btnHigher);

处理程序class: class HigherHandler 实现 ActionListener{

        @Override
        public void actionPerformed(ActionEvent e) {

        }

    }

它只是抛出一个错误: HigherHandler 无法解析为类型

btnHigher = new JButton("Higher");
    btnHigher.setBounds(190, 110, 75, 50);
    btnHigher.addActionListener(new HigherHandler());
    panel.add(btnHigher);

下一行可以这样写,而不是重新写class。

 btnHigher.addActionListener(new HigherHandler(){
       // it will ask you to add implemented method here which is action performed method.

});