java 安全退出 java退出按钮的代码

我需要添加一个“清除计算器”的按钮,以及一个退出butPanel上的程序的按钮.它也需要是非常基本的

Java代码,因为我是初学者,并且有一个糟糕的comp.sci.老师.我有一个带退出按钮的代码示例,但我不确定如何将它放入我的程序中.我已经尝试了这么多.

此外,如果有一个更好的“错误检查”方式,将非常感激.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Calculator2 extends JFrame implements ActionListener
{
JLabel heading = new JLabel ("2. Calculator");
JLabel intro1 = new JLabel ("This program stimulates a four-function calculator.");
JLabel intro2 = new JLabel ("It takes an operator and a number. It can add, subtract,");
JLabel intro3 = new JLabel (" multiply and divide. Enter in the format eg. '+35'. ");
JLabel inLabel = new JLabel (" Operation: ");
JLabel outLabel = new JLabel (" Total: ");
JTextField inOper = new JTextField (7);
JTextField outTota = new JTextField (7); // intro
//panels
JPanel titlePanel = new JPanel ();
JPanel intro1Panel = new JPanel ();
JPanel intro2Panel = new JPanel ();
JPanel intro3Panel = new JPanel ();
JPanel operPanel = new JPanel ();
JPanel totaPanel = new JPanel ();
JPanel butPanel = new JPanel ();
String operTemp;
String totaTemp;
public Calculator2 ()
{
setTitle ("C - 2.");
inOper.addActionListener (this);
outTota.setEditable (false);
getContentPane ().setLayout (new FlowLayout ());
titlePanel.add (heading);
intro1Panel.add (intro1);
intro2Panel.add (intro2);
intro3Panel.add (intro3);
operPanel.add (inLabel);
operPanel.add (inOper);
totaPanel.add (outLabel);
totaPanel.add (outTota); //adds components to panels
getContentPane ().add (titlePanel);
getContentPane ().add (intro1Panel);
getContentPane ().add (intro2Panel);
getContentPane ().add (intro3Panel);
getContentPane ().add (operPanel);
getContentPane ().add (totaPanel); //Adds panels to Frame
setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
}
public static int isInteger (String input)
{
try
{
Integer.parseInt (input);
return Integer.parseInt (input);
}
catch (NumberFormatException nfe)
{
return 0;
}
} //isInteger method
// The application
public String calculate (String operation, String newtotal)
{
int total = isInteger (newtotal);
String totalS;
char operator;
int number = 0;
operator = operation.charAt (0);
if (operator == '+')
{
number = isInteger (operation.substring (1));
total = total + number;
totalS = Integer.toString (total);
}
else if (operator == '-')
{
number = isInteger (operation.substring (1));
total = total - number;
totalS = Integer.toString (total);
}
else if (operator == '*')
{
number = isInteger (operation.substring (1));
total = total * number;
totalS = Integer.toString (total);
}
else if (operator == '/')
{
number = isInteger (operation.substring (1));
total = total / number;
totalS = Integer.toString (total);
}
else
{
totalS = ("ERROR");
}
if (number == 0)
{
totalS = ("ERROR");
}
return totalS;
} // calculate method
public void actionPerformed (ActionEvent evt)
{
String userIn = inOper.getText ();
String totalIn = outTota.getText ();
try
{
totaTemp = calculate (userIn, totalIn);
outTota.setText (totaTemp + "");
}
catch (Exception ex)
{
outTota.setText ("ERROR");
}
repaint ();
}
public static void main (String[] args)
{
Calculator2 calc = new Calculator2 ();
calc.setSize (350, 350);
calc.setResizable (false);
calc.setVisible (true);
}
}