import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.event.*;
public class JiaFa extends JFrame implements ActionListener
{
private JTextField jt1=new JTextField(5);
private JTextField jt2=new JTextField(5);
private JTextField result=new JTextField(5);
private JButton btn=new JButton("=");
JLabel label=new JLabel("+");
public void init(){

Container cp=getContentPane();
cp.setLayout(new FlowLayout(FlowLayout.LEFT));
cp.add(jt1);
cp.add(label);
cp.add(jt2);
cp.add(btn);
cp.add(result);

setSize(300,80);
setVisible(true);

btn.addActionListener(this);
}

public void actionPerformed(ActionEvent e)
{
if(e.getSource()==btn)
{
int a=Integer.parseInt(jt1.getText());
int b=Integer.parseInt(jt2.getText());
int c=a+b;
String str=String.valueOf(c);
result.setText(str);

}
}

public static void main(String args[])
{
JFrame cp=new JiaFa();
cp.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

什么意思啊,原谅我的愚蠢

import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.event.*;
public class JiaFa extends JFrame implements ActionListener
{
private JTextField jt1=new JTextField(5);
private JTextField jt2=new JTextField(5);
private JTextField result=new JTextField(5);
private JButton btn=new JButton("=");
JLabel label=new JLabel("+");
public void into(){

Container cp=this.getContentPane();
cp.setLayout(new FlowLayout(FlowLayout.LEFT));
cp.add(jt1);
cp.add(label);
cp.add(jt2);
cp.add(btn);
cp.add(result);

btn.addActionListener(this);

this.setSize(300,80);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);


}

public void actionPerformed(ActionEvent e)
{

int a=Integer.parseInt(jt1.getText());
int b=Integer.parseInt(jt2.getText());
int c=a+b;
String str=String.valueOf(c);
result.setText(str);

}

public static void main(String args[])
{
JiaFa jf=new JiaFa ();
jf.into();

}
}
你试试　看！界面应该可以出来了！