java实现计算器程序，代码如下：
package code;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.regex.Pattern;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JTextField;
/**
*
* @author Smart
*
*/
public class Calculator extends JFrame implements ActionListener{
private JMenuBar jmb;
private JMenu jm;
private JMenuItem jmi1;
private JTextField result;
private JButton key[];
private JPanel jp_but,jp_cal;
private Mainpad jp_main;
private Container con;
private double opernum;
private String keytitle[]={"7", "8", "9", "+", "4", "5", "6", "-", "1", "2", "3", "*", "0", ".", "=", "/", "!", "^", "C", "-/+", "1/x", "sqrt", "四舍五入", "back"},
opers = "";
public Calculator()
{
this.setSize(400,450);
this.setTitle("计算器");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.jmb=new JMenuBar();
this.jm=new JMenu("文件");
this.jmi1=new JMenuItem("退出");
this.jm.add(this.jmi1);
this.result=new JTextField();
this.key=new JButton[24];
this.jp_but=new JPanel();
this.jp_cal=new JPanel();
this.jp_main=new Mainpad();
this.con=this.getContentPane();
this.jp_but.setLayout(new GridLayout(6,4,5,5));
this.jp_cal.setLayout(new BorderLayout());
this.jp_main.setLayout(new BorderLayout());
this.con.setLayout(new BorderLayout());
Font font = this.result.getFont();
this.result.setFont(new Font(font.getName(), font.getStyle(), 24));
for(int i=0;i<24;i++) {
this.key[i]=new JButton(this.keytitle[i]);
this.key[i].setSize(60, 60);
this.key[i].addActionListener(this);
this.jp_but.add(key[i]);
//System.out.println(i);
}
this.jmb.add(jm);
this.jp_main.add(jmb,BorderLayout.NORTH);
this.jp_main.add(jp_cal,BorderLayout.CENTER);
this.jp_cal.add(result,BorderLayout.NORTH);
this.jp_cal.add(this.jp_but,BorderLayout.CENTER);
this.con.add(jp_main);
this.jmi1.addActionListener(this);
this.setBackground(Color.RED);
this.setLocation(400, 100);
this.setVisible(true);
}
public static void main(String[] args)
{
new Calculator();
}
@Override
public void actionPerformed(ActionEvent evt)
{
// TODO Auto-generated method stub
//System.out.println(evt.getActionCommand());
String oper=evt.getActionCommand();
switch(oper) {
case "0":
this.result.setText(this.result.getText()+oper);
break;
case "1":
this.result.setText(this.result.getText()+oper);
break;
case "2":
this.result.setText(this.result.getText()+oper);
break;
case "3":
this.result.setText(this.result.getText()+oper);
break;
case "4":
this.result.setText(this.result.getText()+oper);
break;
case "5":
this.result.setText(this.result.getText()+oper);
break;
case "6":
this.result.setText(this.result.getText()+oper);
break;
case "7":
this.result.setText(this.result.getText()+oper);
break;
case "8":
this.result.setText(this.result.getText()+oper);
break;
case "9":
this.result.setText(this.result.getText()+oper);
break;
case "+":
this.opernum = Double.valueOf(this.result.getText());
this.result.setText("");
this.opers = "+";
break;
case "-":
this.opernum = Double.valueOf(this.result.getText());
this.result.setText("");
this.opers = "-";
break;
case "*":
this.opernum = Double.valueOf(this.result.getText());
this.result.setText("");
this.opers = "*";
break;
case "/":
this.opernum = Double.valueOf(this.result.getText());
this.result.setText("");
this.opers = "/";
break;
case ".":
this.result.setText(this.result.getText()+oper);
break;
case "^":
this.opernum=Double.valueOf(this.result.getText());
this.result.setText(this.result.getText()+"^");
this.opers="^";
break;
case "-/+":
this.result.setText(String.valueOf(-Double.valueOf(this.result.getText())));
break;
case "1/x":
this.result.setText(String.valueOf(1/(Double.valueOf(this.result.getText()))));
break;
case "sqrt":
this.result.setText(String.valueOf(Math.sqrt(Double.valueOf(this.result.getText()))));
break;
case "四舍五入":
this.result.setText(String.valueOf((int) (Double.valueOf(this.result.getText())+0.5)));
break;
case "back":
if(this.result.getText().length()>0)
this.result.setText(this.result.getText().substring(0, this.result.getText().length()-1));
break;
case "C":
this.result.setText("");break;
case "!":
this.result.setText(String.valueOf(this.JieCheng(Double.valueOf(this.result.getText()))));
break;
case "=":
switch(this.opers) {
case "+":
this.result.setText (String.valueOf(this.opernum+Double.valueOf(this.result.getText())));
break;
case "-":
this.result.setText (String.valueOf(this.opernum-Double.valueOf(this.result.getText())));
break;
case "*":
this.result.setText (String.valueOf(this.opernum*Double.valueOf(this.result.getText())));
break;
case "/":
this.result.setText (String.valueOf(this.opernum/Double.valueOf(this.result.getText())));
break;
case "^":
this.result.setText( String.valueOf((Math.pow(this.opernum, Integer.valueOf(this.result.getText().toString().substring (this.result.getText().toString().indexOf('^')+1))))));
break;
default:
}
break;
case "退出":
System.exit(0);
}
}
public long JieCheng(double n3)
{
long n = (long)(n3 + 0.5);
if(n==1 || n==0)
return n;
else if(n>1) {
return n*JieCheng(n-1);
} else {
return 0;
}
}
public boolean isDot(String num)
{
if(Pattern.matches("[0-9].*", num)) {
return false;
} else {
return true;
}
}
}
class Mainpad extends JPanel{
public Mainpad()
{
this.setBackground(Color.RED);
}
}