Java计算器代码

首先写了个简单的界面如下：



整个面板用了BorderLayout布局，分为北，左和中。中部采用网格布局。定义这个类为CalFrame.java:

[java] view
plain copy

package calframe;

import java.awt.BorderLayout;

import java.awt.Color;

import java.awt.Dimension;

import java.awt.GridLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.util.Arrays;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JTextField;

public class CalFrame extends JFrame {

/**

* 计算器的外观设计

*/

private static final long serialVersionUID = 1L;

private final static int PRE_WIDTH = 500;

private final static int PRE_HEIGHT = 400;

private JTextField text = null;

private JButton button = null; //存储标记

private String[] nOp = {"7","8","9","/","sqrt","4","5","6","*","%","1","2","3","-","1/x","0","+/-",".","+","="};

private String[] mOp = {"MC","MR","MS","M+"};

private String[] rOp = {"Back","CE","C"};

private CalService service = new CalService();

public CalFrame(){

this.setTitle("计算器");

this.setSize(PRE_WIDTH, PRE_HEIGHT);

this.setLocationRelativeTo(null);

this.setResizable(false);

//添加底层

JPanel panel = new JPanel();

panel.setLayout(new BorderLayout(10,1));

panel.add(getTextField(), BorderLayout.NORTH);

panel.setPreferredSize(new Dimension(PRE_WIDTH, PRE_HEIGHT));

//WEST

JButton[] mButton = getMButton();

JPanel panel1 = new JPanel();

panel1.setLayout(new GridLayout(5,1,0,5));

for(JButton b : mButton ){

panel1.add(b);

}

panel.add(panel1,BorderLayout.WEST);

//

JButton[] rButton = getRButton();

JPanel panel2 = new JPanel();

panel2.setLayout(new BorderLayout(1,5));

JPanel panel21 = new JPanel();

panel21.setLayout(new GridLayout(1,3,3,3));

for(JButton b : rButton){

panel21.add(b);

}

panel2.add(panel21,BorderLayout.NORTH);

JButton[] nButton = getNButton();

JPanel panel22 = new JPanel();

panel22.setLayout(new GridLayout(4,5,3,5));

for(JButton b : nButton){

panel22.add(b);

}

panel2.add(panel22,BorderLayout.CENTER);

panel.add(panel2,BorderLayout.CENTER);

this.add(panel);

this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

this.setVisible(true);

}

//返回显示框

private JTextField getTextField(){

text = new JTextField("0",10);

//text.setSize(480, 50);

return text;

}

//返回数字键

private JButton[] getNButton(){

String[] redButton = {"/","*","-","+","="};

JButton[] nbutton = new JButton[nOp.length];

for(int i = 0; i < this.nOp.length; i++){

JButton b = new JButton(this.nOp[i]);

b.addActionListener(getActionListener());

Arrays.sort(redButton);

if(Arrays.binarySearch(redButton, nOp[i]) >= 0){

b.setForeground(Color.red);

}else{

b.setForeground(Color.blue);

}

nbutton[i] = b;

}

return nbutton;

}

//返回操作健

private JButton[] getMButton(){

JButton[] mbutton = new JButton[mOp.length + 1];

mbutton[0] = getButton();

for(int i = 0; i < this.mOp.length; i++){

JButton b = new JButton(this.mOp[i]);

b.addActionListener(getActionListener());

b.setForeground(Color.red);

mbutton[i+1] = b;

}

return mbutton;

}

private JButton[] getRButton(){

JButton[] rbutton = new JButton[rOp.length];

for(int i = 0; i < this.rOp.length; i++){

JButton b = new JButton(this.rOp[i]);

b.addActionListener(getActionListener());

b.setForeground(Color.red);

rbutton[i] = b;

}

return rbutton;

}

private JButton getButton(){

button = new JButton();

return button;

}

private ActionListener getActionListener(){

ActionListener actionListener = new ActionListener() {

@Override

public void actionPerformed(ActionEvent e) {

String cmd = e.getActionCommand();

String result = null;

try {

result = service.callMethod(cmd, text.getText());

} catch (Exception e2) {

System.out.println(e2.getMessage());

}

if(cmd.indexOf("MC") == 0){

button.setText("");

}else if(cmd.indexOf("M") == 0){

button.setText("M");

}

//显示计算结果

if(result != null){

text.setText(result);

}

}

};

return actionListener;

}

public static void main(String[] args) {

new CalFrame();

}

}

接着实现几个基本的操作，加，减，乘，除。考虑到精度和范围的问题，我们定义了一个MyMath类，数据格式都使用BigDecimal对象进行计算。MyMath.java:

[java] view
plain copy

package calframe;

import java.math.BigDecimal;

public class MyMath {

/**

* 为一个double类型创建BigDecimal对象

*/

private static BigDecimal getBigDecimal(double number){

return new BigDecimal(number);

}

public static double add(double num1, double num2) {

BigDecimal first = getBigDecimal(num1);

BigDecimal second = getBigDecimal(num2);

return first.add(second).doubleValue();

}

public static double subtract(double num1, double num2) {

BigDecimal first = getBigDecimal(num1);

BigDecimal second = getBigDecimal(num2);

return first.subtract(second).doubleValue();

}

public static double multiply(double num1, double num2) {

BigDecimal first = getBigDecimal(num1);

BigDecimal second = getBigDecimal(num2);

return first.multiply(second).doubleValue();

}

public static double divide(double num1, double num2) {

BigDecimal first = getBigDecimal(num1);

BigDecimal second = getBigDecimal(num2);

return first.divide(second,3,BigDecimal.ROUND_HALF_UP).doubleValue();

}

}

最后处理按钮的事件，我们定义了一个CalService类处理业务逻辑：

[java] view
plain copy

package calframe;

public class CalService {

private boolean isSecondNum = false;

private String lastOp;

private String firstNum = "0";

private String secondNum = "null";

private double store;

private String numString = "0123456789.";

private String opString = "+-*/";

public String catNum(String cmd, String text) {

String result = cmd;

// 如果text不等于0

if (!"0".equals(text)) {

if (isSecondNum) {

isSecondNum = false;

} else {

result = text + cmd;

}

}

if (result.indexOf(".") == 0) {

result = "0" + result;

}

return result;

}

public String setOp(String cmd, String text) {

this.lastOp = cmd;

this.firstNum = text;

this.secondNum = null;

this.isSecondNum = true;

return null;

}

public String cal(String text, boolean isPercent) {

double secondResult = secondNum == null ? Double.valueOf(text)

.doubleValue() : Double.valueOf(secondNum).doubleValue();

//除数为0

if(secondResult == 0 && this.lastOp.equals("/")){

return "0";

}

//有%

if(isPercent){

secondResult = MyMath.multiply(Double.valueOf(firstNum), MyMath.divide(secondResult, 100));

}

if(this.lastOp.equals("+")){

firstNum = String.valueOf(MyMath.add(Double.valueOf(firstNum),secondResult));

}else if (this.lastOp.equals("-")) {

firstNum = String.valueOf(MyMath.subtract(Double.valueOf(firstNum),secondResult));

}else if (this.lastOp.equals("*")) {

firstNum = String.valueOf(MyMath.multiply(Double.valueOf(firstNum),secondResult));

}else if (this.lastOp.equals("/")) {

firstNum = String.valueOf(MyMath.divide(Double.valueOf(firstNum),secondResult));

}

secondNum = secondNum == null ? text :secondNum;

this.isSecondNum = true;

return firstNum;

}

//求开方

public String sqrt(String text){

this.isSecondNum = true;

return String.valueOf(Math.sqrt(Double.valueOf(text)));

}

//求倒数

public String setReciprocal(String text){

if (text.equals("0")){

return text;

}else{

this.isSecondNum = true;

return String.valueOf(MyMath.divide(1, Double.valueOf(text)));

}

}

//存储

public String mCmd(String cmd,String text){

if(cmd.equals("M+")){

store = MyMath.add(store, Double.valueOf(text));

}else if (cmd.equals("MC")) {

store = 0;

}else if (cmd.equals("MR")) {

isSecondNum = true;

return String.valueOf(store);

}else if (cmd.equals("MS")) {

store = Double.valueOf(text).doubleValue();

}

return null;

}

public String backSpace(String text){

return text.equals("0") || text.equals("") ? "0" :text.substring(0,text.length()-1);

}

public String setNegative(String text){

if(text.indexOf("-") == 0){

return text.substring(1,text.length());

}else{

return "-" + text;

}

}

public String clearAll(){

this.firstNum = "0";

this.secondNum = null;

return this.firstNum;

}

public String clear(String text){

return "0";

}

public String callMethod(String cmd, String text){

if(cmd.equals("C")){

return clearAll();

}else if(cmd.equals("CE")){

return clear(text);

}else if (cmd.equals("Back")) {

return backSpace(text);

}else if (numString.indexOf(cmd) != -1) {

return catNum(cmd, text);

}else if (opString.indexOf(cmd) != -1) {

return setOp(cmd, text);

}else if (cmd.equals("+/-")) {

return setNegative(text); //设置正负号

}else if(cmd.equals("1/x")){

return setReciprocal(text);

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

return sqrt(text);

}else if(cmd.equals("%")){

return cal(text, true);

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

return cal(text, false);

}else {

return mCmd(cmd, text);

}

}

}

最后的calMethod方法大量使用if else判断不是好的实现方法，感兴趣的可以看看java的设计模式，消除这样的判断。

至此，一个简易的计算器就完成了。欢迎大家给为留言，共同学习，共同进步。