如何用JAVA语言编写计算器小程序？

具体代码如下：

import javax.swing.*

import java.awt.event.*

import java.awt.*

public class Calculator  extends JFrame implements ActionListener  {

private JFrame jf

private JButton[] allButtons

private JButton clearButton

private JTextField jtf

public Calculator() {

//对图形组件实例化

jf=new JFrame("任静的计算器1.0：JAVA版")

jf.addWindowListener(new WindowAdapter(){

public void windowClosing(){

System.exit(0)

}

})

allButtons=new JButton[16]

clearButton=new JButton("清除")

jtf=new JTextField(25)

jtf.setEditable(false)

String str="123+456-789*0.=/"

for(int i=0i<allButtons.lengthi++){

allButtons[i]=new JButton(str.substring(i,i+1))

}

}

public void init(){

//完成布局

jf.setLayout(new BorderLayout())

JPanel northPanel=new JPanel()

JPanel centerPanel=new JPanel()

JPanel southPanel=new JPanel()

northPanel.setLayout(new FlowLayout())

centerPanel.setLayout(new GridLayout(4,4))

southPanel.setLayout(new FlowLayout())

northPanel.add(jtf)

for(int i=0i<16i++){

centerPanel.add(allButtons[i])

}

southPanel.add(clearButton)

jf.add(northPanel,BorderLayout.NORTH)

jf.add(centerPanel,BorderLayout.CENTER)

jf.add(southPanel,BorderLayout.SOUTH)

addEventHandler()

}

//添加事件监听

public void addEventHandler(){

jtf.addActionListener(this)

for(int i=0i<allButtons.lengthi++){

allButtons[i].addActionListener(this)

}

clearButton.addActionListener(new ActionListener(){

public void actionPerformed(ActionEvent e) {

// TODO Auto-generated method stub

Calculator.this.jtf.setText("")

}

})

}

//事件处理

public void actionPerformed(ActionEvent e) {

//在这里完成事件处理  使计算器可以运行

String action=e.getActionCommand()

if(action=="+"||action=="-"||action=="*"||action=="/"){

}

}

public void setFontAndColor(){

Font f=new Font("宋体",Font.BOLD,24)

jtf.setFont(f)

jtf.setBackground(new Color(0x8f,0xa0,0xfb))

for(int i=0i<16i++){

allButtons[i].setFont(f)

allButtons[i].setForeground(Color.RED)

}

}

public void showMe(){

init()

setFontAndColor()

jf.pack()

jf.setVisible(true)

jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)

}

public static void main(String[] args){

new Calculator().showMe()

}

}

import java.awt.*

import java.awt.event.*

class CalcAppDemo extends Frame{

private TextField t_result

private Panel p_main//主面板

private Panel p_num//数字面板

private Panel p_oper// *** 作符面板

private Panel p_show//显示面板

private Button b_num[]//数字按钮

private Button b_oper[]// *** 作符按钮

public CalcAppDemo(String title){

setTitle(title)

t_result = new TextField("0.0",21)

p_main = new Panel()

p_num = new Panel()

p_oper = new Panel()

p_show = new Panel()

p_main.setLayout(new BorderLayout())

p_num.setLayout(new GridLayout(4,3,1,1))

p_oper.setLayout(new GridLayout(4,2,1,1))

b_num = new Button[12]

for(int i = 0i <9i++){

b_num[i] = new Button(new Integer(i+1).toString())

}

b_num[9] = new Button("0")

b_num[10] = new Button("cls")

b_num[11] = new Button(".")

for(int i = 0i <12i++){

p_num.add(b_num[i])

}

b_oper = new Button[8]

b_oper[0] = new Button("+")

b_oper[1] = new Button("-")

b_oper[2] = new Button("*")

b_oper[3] = new Button("/")

b_oper[4] = new Button("pow")

b_oper[5] = new Button("sqrt")

b_oper[6] = new Button("+/-")

b_oper[7] = new Button("=")

for(int i = 0i <8i++){

p_oper.add(b_oper[i])

}

t_result.setEditable(false)

p_show.add(t_result,BorderLayout.NORTH) //文本框在显示面板的北边

p_main.add(p_show,BorderLayout.NORTH) //显示面板在主面板上的北边

p_main.add(p_num,BorderLayout.WEST)

p_main.add(p_oper,BorderLayout.EAST)// *** 作符面板在主面板上的东边

this.add(p_main,BorderLayout.CENTER)//主面板在框架（主窗口）的中间

setSize(400,400)

setResizable(false)

pack()

this.addWindowListener(new WindowAdapter(){

public void windowClosing(WindowEvent e){

System.exit(0)

}

})

ButtonListener bl = new ButtonListener() //监听器对象

for(int i=0i<12i++){

b_num[i].addActionListener(bl) //注册监听器

}

for(int i = 0i <8i++){

b_oper[i].addActionListener(bl)

}

}

class ButtonListener implements ActionListener { //监听器类是内部类

private String lastOp//存储上一次 *** 作符

private String strVal//存储数字对应的字符串

private double total//总数

private double number//存储新输入的数

private boolean firsttime//判断是否第一次按下的是 *** 作符按钮

private boolean operatorPressed//判断是否已经按过 *** 作符按钮

ButtonListener( ){

firsttime = true

strVal = ""

}

//事件处理器

public void actionPerformed( ActionEvent e ){

String s = ((Button)e.getSource()).getLabel().trim()

if(Character.isDigit(s.charAt(0))){//判断是 *** 作数还是 *** 作符

handleNumber(s)

}else{

calculate(s) //计算

}

}

//判断是一元 *** 作符还是二元 *** 作符，并根据 *** 作符类型做计算

void calculate( String op ){

operatorPressed = true

if(firsttime&&!isUnary(op)){

total = getNumberOnDisplay()

firsttime = false

}

if (isUnary(op)){

handleUnaryOp(op)

}

else if (lastOp != null){

handleBinaryOp(lastOp)

}

if (!isUnary(op)){ //存储上一次按下的 *** 作符

lastOp = op

}

}

//判断是否是一元 *** 作符

boolean isUnary(String s){

returns.equals( "=" )

|| s.equals( "cls" )

|| s.equals( "sqrt" )

|| s.equals( "+/-" )

|| s.equals( "." )

}

//处理一元 *** 作符

void handleUnaryOp( String op ){

if ( op.equals( "+/-" ) ){

//将显示框中的数字取反

number = negate(getNumberOnDisplay()+"")

t_result.setText("")

t_result.setText( number + "")

return

}else if (op.equals(".")){

handleDecPoint()

return

}else if(op.equals("sqrt")){

number = Math.sqrt(getNumberOnDisplay())

t_result.setText("")

t_result.setText(number+"")

return

}else if(op.equals("=")){

//在按下"="前已经按下一个二元运算符

if(lastOp!=null&&!isUnary(lastOp)){

handleBinaryOp(lastOp)

}

lastOp=null

firsttime=true

return

}else{

clear()

}

}

//处理二元运算符

void handleBinaryOp(String op){

if(op.equals("+")){

total += number

}else if(op.equals("-")){

total -= number

}else if(op.equals("*")){

total *= number

}else if(op.equals("/")){

try{ //异常处理

total /=number

}catch(ArithmeticException ae){}

}else if(op.equals("pow"))

total=Math.pow(total,number)

// t_result.setText("")

lastOp = null

// strVal = ""

number = 0

t_result.setText(total+"")

}

//该方法用于处理数字按钮

void handleNumber(String s){

if (!operatorPressed){ //连接按下的数字按钮的值

strVal+=s

}

else{//当按下 *** 作符按钮时，清除strVal并存储输入的第一个数值

operatorPressed = false

strVal = s

}

//将strVal转换为double

number=new Double(strVal).doubleValue()

t_result.setText("")

t_result.setText(strVal)

}

//该方法用于按下"."按钮

void handleDecPoint(){

operatorPressed = false

//如果该字符串中无"."，放置一个"."在字符串末尾

if ( strVal.indexOf( "." ) <0 ) {

strVal+="."

}

t_result.setText("")

t_result.setText( strVal )

}

//该方法用于将一个数求反

double negate( String s ){

operatorPressed = false

//如果是一个整数，去掉小数点后面的0

if ( number == ( int ) number ){

s = s.substring(0, s.indexOf( "." ) )

}

//如果无"-"增加在该数的前面

if ( s.indexOf( "-" ) <0 ){

strVal = "-"+s

}

else{//如果有"-"则去掉

strVal = s.substring( 1 )

}

return new Double( strVal ).doubleValue()

}

//将显示框中的值转换为Double

double getNumberOnDisplay() {

return new Double(t_result.getText()).doubleValue()

}

//清除屏幕并设置所有的标识

void clear(){

firsttime = true

lastOp = null

strVal = ""

total = 0

number = 0

t_result.setText("0")

}

}

public static void main(String args[]){

CalcAppDemo c = new CalcAppDemo("简单的计算器程序")

c.setVisible(true)

}

}

//这是我以前写的，参考一下吧

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