找错误package text5;//窗口类 import java.awt.*; import javax.swing.*; import java.awt.event.*; public class e9_1 { public static void main(String args[]) { PoliceWindow policeWin=new PoliceWindow(); } } class PoliceWindow extends JFrame { JTextField titleText; JPasswordField passwordText; PoliceWindow() { titleText=new JTextField(10); passwordText=new JPasswordField(10); passwordText.setEchoChar('*'); titleText.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { JTextField textSourse=(JTextField)e.getSource(); if(textSourse==titleText) PoliceWindow.setTitle(titleText.getText()); else if(textSourse==passwordText){ char c[]=passwordText.getPassword(); titleText.setText(new String(c)); } }); passwordText.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { JTextField textSourse=(JTextField)e.getSource(); if(textSourse==titleText) PoliceWindow.setTitle(titleText.getText()); else if(textSourse==passwordText){ char c[]=passwordText.getPassword(); titleText.setText(new String(c)); } }); setLayout(new FlowLayout()); add(titleText); add(passwordText); setBounds(100,100,150,150); setVisible(true); validate(); setDefaultCloseOperation(DISPOSE_ON_CLOSE); } } }

错误是在 `PoliceWindow` 类的构造函数中，第一个 `addActionListener` 方法和第二个 `addActionListener` 方法的代码完全相同，应该分别定义不同的功能。以下是修改后的代码：

package text5;

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class e9_1 {

    public static void main(String args[]) {
        PoliceWindow policeWin = new PoliceWindow();
    }
}

class PoliceWindow extends JFrame {
    JTextField titleText;
    JPasswordField passwordText;

    PoliceWindow() {
        titleText = new JTextField(10);
        passwordText = new JPasswordField(10);
        passwordText.setEchoChar('*');

        // 监听标题文本框
        titleText.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JTextField textSource = (JTextField) e.getSource();
                if (textSource == titleText)
                    PoliceWindow.this.setTitle(titleText.getText());
            }
        });

        // 监听密码文本框
        passwordText.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JTextField textSource = (JTextField) e.getSource();
                if (textSource == passwordText) {
                    char c[] = passwordText.getPassword();
                    titleText.setText(new String(c));
                }
            }
        });

        setLayout(new FlowLayout());
        add(titleText);
        add(passwordText);
        setBounds(100, 100, 150, 150);
        setVisible(true);
        validate();
        setDefaultCloseOperation(DISPOSE_ON_CLOSE);
    }
}