用JAVA做一个计算器

import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;

public class Jisuanqi extends JFrame implements ActionListener {
Result result = new Result(); //定义text的面板
Number_Key number_key = new Number_Key(); //定义按钮面板
//当点击按钮+、-、*、/时，com = true
boolean com = false;

//当i=0时说明是我们第一次输入，字符串text不会累加
int i = 0;

//存放text的内容
String text = "";

//存放点击按钮+、-、*、/之前的数值
double defbutton = 0;

//+、-、*、/的代号分别为1，2，3，4
int symbol = 0;

//构造函数
Jisuanqi() {
super("WangJiao"); //设定标题
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //设定关闭窗体时退出程序
JPanel pane = new JPanel(); //定义主面板

pane.setLayout(new BorderLayout());
setBounds(380,220,30,80); //前两个参数是在屏幕上显示的坐标，后两个是大小

//替换图标
ImageIcon icon=new ImageIcon(
Jisuanqi.class.getResource("APPLE.GIF")
);
setIconImage(icon.getImage());

pane.add(result, BorderLayout.NORTH);
pane.add(number_key, BorderLayout.CENTER);
pane.add(number_key.equal, BorderLayout.SOUTH);

number_key.one.addActionListener(this); //对1按钮添加监听事件
number_key.two.addActionListener(this); //对2按钮添加监听事件
number_key.three.addActionListener(this); //对3按钮添加监听事件
number_key.four.addActionListener(this); //对4按钮添加监听事件
number_key.five.addActionListener(this); //对5按钮添加监听事件
number_key.six.addActionListener(this); //对6按钮添加监听事件
number_key.seven.addActionListener(this); //对7按钮添加监听事件
number_key.eight.addActionListener(this); //对8按钮添加监听事件
number_key.nine.addActionListener(this); //对9按钮添加监听事件
number_key.zero.addActionListener(this); //对0按钮添加监听事件
number_key.ce.addActionListener(this); //对置零按钮添加监听事件
number_key.plus.addActionListener(this); //对+按钮添加监听事件
number_key.equal.addActionListener(this); //对=按钮添加监听事件
number_key.sub.addActionListener(this); //对-按钮添加监听事件
number_key.mul.addActionListener(this); //对*按钮添加监听事件
number_key.div.addActionListener(this); //对/按钮添加监听事件
number_key.point.addActionListener(this); //对.按钮添加监听事件

setContentPane(pane);
pack(); //初始化窗体大小为正好盛放所有按钮
}

//各个按钮触发的事件
public void actionPerformed(ActionEvent e) {

/*如果是点击数字按钮那么先要判断是否在此之前点击了+、-、*、/、=，如果是那么com=true
* 如果没有com= false;或者是否点击数字键，如果是i = 1,如果没有 i = 0;
**/
if (e.getSource() == number_key.one) {
if (com || i == 0) {
result.text.setText("1");
com = false;
i = 1;
} else {
text = result.text.getText();
result.text.setText(text + "1");
}
} else if (e.getSource() == number_key.two) {
if (com || i == 0) {
result.text.setText("2");
com = false;
i = 1;
} else {
text = result.text.getText();
result.text.setText(text + "2");
}

} else if (e.getSource() == number_key.three) {
if (com || i == 0) {
result.text.setText("3");
com = false;
i = 1;
} else {
text = result.text.getText();
result.text.setText(text + "3");
}
} else if (e.getSource() == number_key.four) {
if (com || i == 0) {
result.text.setText("4");
com = false;
i = 1;
} else {
text = result.text.getText();
result.text.setText(text + "4");
}
} else if (e.getSource() == number_key.five) {
if (com || i == 0) {
result.text.setText("5");
com = false;
i = 1;
} else {
text = result.text.getText();
result.text.setText(text + "5");
}
} else if (e.getSource() == number_key.six) {
if (com || i == 0) {
result.text.setText("6");
com = false;
i = 1;
} else {
text = result.text.getText();
result.text.setText(text + "6");
}
} else if (e.getSource() == number_key.seven) {
if (com || i == 0) {
result.text.setText("7");
com = false;
i = 1;
} else {
text = result.text.getText();
result.text.setText(text + "7");
}
} else if (e.getSource() == number_key.eight) {
if (com || i == 0) {
result.text.setText("8");
com = false;
i = 1;
} else {
text = result.text.getText();
result.text.setText(text + "8");
}
} else if (e.getSource() == number_key.nine) {
if (com || i == 0) {
result.text.setText("9");
com = false;
i = 1;
} else {
text = result.text.getText();
result.text.setText(text + "9");
}
}

/*对于0这个按钮有一定的说法，在我的程序里不会出现如00000这样的情况，我加了判断条件就是
* 如果text中的数值=0就要判断在这个数值中是否有.存在?如果有那么就在原来数值基础之上添
* 加0;否则保持原来的数值不变
*/
else if (e.getSource() == number_key.zero) { //result.text.getText()是得到text里内容的意思
if (com || i == 0) {
result.text.setText("0");
com = false;
i = 1;
} else {
text = result.text.getText();
if (Float.parseFloat(text) > 0 || Float.parseFloat(text) < 0) { //Float.parseFloat(text)就是类型转换了，下面都是一样
result.text.setText(text + "0");
} else {
if (text.trim().indexOf(".") == -1) {
result.text.setText(text);
} else {
result.text.setText(text + "0");
}
}
}
} else if (e.getSource() == number_key.ce) {
result.text.setText("0");
i = 0;
com = true;
}
/*本程序不会让一个数值中出现2个以上的小数点.具体做法是:判断是否已经存在.存在就不添加,
* 不存在就添加.
*/
else if (e.getSource() == number_key.point) {
if (com || i == 0) {
result.text.setText("0.");
com = false;
i = 1;
} else {
text = result.text.getText();
if (text.trim().indexOf(".") == -1) {
result.text.setText(text + ".");
} else {
result.text.setText(text);
}

}
} //获得点击+之前的数值
else if (e.getSource() == number_key.plus) {
com = true;
i = 0;
defbutton = Double.parseDouble(result.text.getText());
symbol = 1;
} //获得点击-之前的数值
else if (e.getSource() == number_key.sub) {
com = true;
i = 0;
defbutton = Double.parseDouble(result.text.getText());

symbol = 2;
} //获得点击*之前的数值
else if (e.getSource() == number_key.mul) {
com = true;
i = 0;
defbutton = Double.parseDouble(result.text.getText());
System.out.println(defbutton);
symbol = 3;
} //获得点击/之前的数值
else if (e.getSource() == number_key.div) {
com = true;
i = 0;
defbutton = Double.parseDouble(result.text.getText());
symbol = 4;
} else if (e.getSource() == number_key.equal) {

switch (symbol) {
case 1 : //计算加法
{
double ad =
defbutton + Double.parseDouble(result.text.getText());
result.text.setText(ad + "");
i = 0;
text = "";
break;
}
case 2 ://计算减法
{
double ad =
defbutton - Double.parseDouble(result.text.getText());
result.text.setText(String.valueOf(ad));
i = 0;
text = "";
break;
}
case 3 ://计算乘法
{
double ad =
defbutton * Double.parseDouble(result.text.getText());

result.text.setText(ad + "");
i = 0;
text = "";
break;
}
case 4 ://计算除法
{
double ad =
defbutton / Double.parseDouble(result.text.getText());
result.text.setText(ad + "");
i = 0;
text = "";
break;
}
}

System.out.println(com);
}
}

public static void main(String[] args) {
Jisuanqi loveyou = new Jisuanqi();
loveyou.show();
}
}

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

//计算器数字按钮定义面板
class Number_Key extends JPanel {

JButton zero = new JButton("0"); //数字键0
JButton one = new JButton("1"); //数字键1
JButton two = new JButton("2"); //数字键2
JButton three = new JButton("3"); //数字键3
JButton four = new JButton("4"); //数字键4
JButton five = new JButton("5"); //数字键5
JButton six = new JButton("6"); //数字键6
JButton seven = new JButton("7"); //数字键7
JButton eight = new JButton("8"); //数字键8
JButton nine = new JButton("9"); //数字键9

JButton plus = new JButton("+");
JButton sub = new JButton("-");
JButton mul = new JButton("*");
JButton div = new JButton("/");
JButton equal = new JButton("=");
JButton ce = new JButton("清零"); //置零键
JButton point = new JButton(".");

Number_Key() {
setLayout(new GridLayout(4, 4, 1, 1)); //定义布局管理器为网格布局

setBackground(Color.blue); //设置背景颜色
//添加按钮
add(one);
add(two);
add(three);
add(four);
add(five);
add(six);
add(seven);
add(eight);
add(nine);
add(zero);
add(plus);
add(sub);
add(mul);
add(div);
add(point);
add(equal);
add(ce);
}
}

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

//计算器显示结果的窗体
class Result extends JPanel {
//text先是输入和结果
JTextField text = new JTextField("0");

Result() { //讲输入的数字或得到的结果在text的右边显示
text.setHorizontalAlignment(SwingConstants.RIGHT);
text.enable(false); //文本框不能编辑
setLayout(new BorderLayout()); //设定布局管理器边框布局
add(text, BorderLayout.CENTER); //text放置在窗体的中间
}
}