编译出错，不解？请高手指点。

[kempguan]

源码：
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
class Undo
{
JFrame frame;
public void Undo(String str){
frame = new JFrame(str);
frame.addWindowListener(new WindowAdapter(){public void windowClosing(WindowEvent e){System.exit(0);}});
frame.getContentPane().setLayout(null);
frame.setSize(300,400);
frame.setVisible(true);
}
public static void main(String[] args)
{
Undo n=new Undo("Undo");
}
}

出错信息：constructor中的参数数量错误。
Undo n= new Undo("Undo");
^

[bdsc]

构造函数没有返回类型

[kempguan]

谢谢，这点问题怎么没想到。

[jianghuxiaozi]

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
class Undo
{
JFrame frame;
public Undo(String str){
frame = new JFrame(str);
frame.addWindowListener(new WindowAdapter(){public void windowClosing(WindowEvent e){System.exit(0);}});
frame.getContentPane().setLayout(null);
frame.setSize(300,400);
frame.setVisible(true);
}
public static void main(String[] args)
{
Undo n=new Undo("Undo");
}
}

[Whyin]

把:
public void Undo(String str){
中的void 去掉，因为Undo()是构造涵数，初始话，应该
public Undo(String str) 声明就可以了