在 Java 中使用 Swing 时显示错误消息的对话框

Question

我不是一个好的Java程序员。当我使用这种编码时，我遇到了一些错误。有人可以帮我吗？

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.JOptionPane;
public class test4 implements ActionListener
{
    public static void main(String[] args)throws Exception
    {
        JFrame f=new JFrame("test 4");
        JButton b=new JButton("gud morning");
        JButton b1=new JButton("yes or no");
        b.addActionListener(this);
        b1.addActionListener(this);
        Container content=f.getContentPane();
        content.add(b,BorderLayout.NORTH);
        content.add(b1,BorderLayout.SOUTH);
        f.setVisible(true);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setSize(100,100);
        }
}
public void actionPerformed(ActionEvent e)
{
    String s=e.getActionCommand();
    if(s.equals("gud morning"))
    {
        JOptionPane.showMessageDialog(f,"gud morning","My Message");
    }
    else if(s.equals("yes or no"))
    {

        if(JOptionPane.showConfirmMessageDialog(f,"yes or no","it is also my message",JOptionPane.YES_NO_CANCEL_OPTION)==0);
        {
            JOptionPane.showMessageDialog(f,"u clicked yes button");
        }
        else
        {
            JOptionPane.showMessageDialog(f,"u clicked no button");
        }
    }
}

我收到此错误：

ram>javac test4.java test4.java:22: error: class, interface, or enum expected public void actionPerformed(ActionEvent e) ^ test4.java:25: error: class, interface, or enum expected if(s.equals("gud morning")) ^ test4.java:28: error: class, interface, or enum expected } ^ 3 errors

Answer 1

您的if语句被一个;所干扰，这将使else分支不正确。删除;

if(JOptionPane.showConfirmMessageDialog(f,"yes or no","it is also my message",JOptionPane.YES_NO_CANCEL_OPTION)==0);

成为：

if(JOptionPane.showConfirmMessageDialog(f,"yes or no","it is also my message",JOptionPane.YES_NO_CANCEL_OPTION)==0)

在actionPerformed开始之前，您还有一个额外的花括号}。