import java.awt.*;
import javax.swing.*;
public class TextFieldDemo extends JFrame {
public TextFieldDemo(String s) {
s="*";
Container con=getContentPane();
con.setLayout(new FlowLayout());
JLabel jl = new JLabel("密码：");
con.add(jl);
JTextField tf = new JTextField(16);
con.add(tf);
setSize(300,200);
setVisible(true);
}

public static void main(String args[]) {
new TextFieldDemo();
}

}


请问下 让文本框里的内容为***** 是不是这样写? 这个有错误但是不知道怎么改 请指教!!!

import java.awt.*;
import javax.swing.*;
public class TextFieldDemo extends JFrame {
public TextFieldDemo(){
Container con=getContentPane();
con.setLayout(new FlowLayout());
JLabel jl = new JLabel("密码：");
con.add(jl);
JTextField tf = new JTextField(16);
con.add(tf);
setSize(300,200);
setVisible(true);
}

public class JPasswordField extends TextFieldDemo(String s) {
s="*";
}
public static void main(String args[]) {
new TextFieldDemo();
new JPasswordField();

}
}






那就是这样 ?

用了以后他出了个提示
错误: 无法读取 :JPasswordField.java