怎么添加事件

我的Java代码怎么添加事件：点击“加水”，“请加水”就变成“不需要加水”

public class Left {
private JLabel textWater = new JLabel("请加水");
private JPanel panel1 = new JPanel();

public Left(){
    panel1.add(textWater);
}

public JPanel getPanel1() {
    return panel1;
}

public void setPanel1(JPanel panel1) {
    this.panel1 = panel1;
}
}
public class Right{
private JButton addwater = new JButton("加水");
private JPanel panel3 = new JPanel();

public Right(){
    panel3.add(addwater);
}

public JPanel getPanel3() {
    return panel3;
}

public void setPanel3(JPanel panel3) {
    this.panel3 = panel3;
}
}
public class Test extends JFrame{
public Test(){
    super("咖啡机");
    this.setSize(200,200);
    this.setLayout(new FlowLayout());
    Left left = new Left();
    Right right = new Right();
    this.add(left.getPanel1());
    this.add(right.getPanel3());
    this.setLocationRelativeTo(null);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setVisible(true);
}
public static void main(String[] args) {
    new Test();
}
}

点击“加水”，“请加水”就变成“不需要加水”.