要求：
1.使用Java图形界面组件设计软件，界面如图所示。
2.软件能够满足基本的“加、减、乘、除”等运算要求。
3.程序代码清晰，语法规范，结构合理，逻辑正确。
效果图：
先分析，计算器大概是由三个大部分组成的：菜单栏，显示框，按钮。
所以定义一个类cal继承JFrame。
class cal extends JFrame{private JPanel p1, p2;private JTextArea show;private String box ;JMenuBar menubar;//菜单JMenu menu1, menu2, menu3;//菜单StringBuffer strA;//用来存放用户输入的第一个数字StringBuffer strB;//用来存放用户输入的第二个数字char oper ='~';//初始化操作符，可以随便初始化一个特殊符号，这里只是用来区分的doubleA;doubleB;private String[] text2 = {"C", "CE","%", "/","7", "8", "9", "*","4", "5", "6", "-","1", "2", "3", "+","DEL","0", ".", "="};//计算器按钮面板private JButton[] munButton = new JButton[text2.length];}我们定义完后开始初始化。
class cal extends JFrame implements ActionListener {private JPanel p1, p2;private JTextArea show;private String box ;JMenuBar menubar;JMenu menu1, menu2, menu3;StringBuffer strA;StringBuffer strB;char oper ='~';doubleA;doubleB;private String[] text2 = {"C", "CE","%", "/","7", "8", "9", "*","4", "5", "6", "-","1", "2", "3", "+","DEL","0", ".", "="};//计算器按钮面板private JButton[] munButton = new JButton[text2.length];public cal() {p1 = new JPanel();p2 = new JPanel();show = new JTextArea();p1.setSize(600, 100);menubar = new JMenuBar();menu1 = new JMenu("查看(V)");menu2 = new JMenu("编辑(E)");menu3 = new JMenu("帮助(H)");strB=new StringBuffer();strA=new StringBuffer();}public void init() {//初始化this.setTitle("计算器");//设置名称this.setBounds(200, 200, 320, 300);this.setLayout(new BorderLayout());//设置布局this.add(p1, BorderLayout.CENTER);this.add(p2, BorderLayout.SOUTH);menubar.add(menu1);menubar.add(menu2);menubar.add(menu3);this.setJMenuBar(menubar);this.setLocationRelativeTo(null);//放置在屏幕中央this.setResizable(false);//固定大小，用户不能调整大小show.setPreferredSize(new Dimension(300, 100));p1.add(show);p2.setLayout(new GridLayout(5, 4, 2, 3));//添加数字按键for (int i = 0; i < text2.length; i++) {munButton[i] = new JButton(text2[i] + " ");p2.add(munButton[i]);}for (int i = 0; i < munButton.length; i++)munButton[i].addActionListener(this);this.setVisible(true);//窗体可视化this.addWindowListener(new WindowAdapter() {//监听事件，当按下关闭按钮时，结束程序@Overridepublic void windowClosing(WindowEvent e) {System.exit(0);}});}接着我们就开始进入到这个项目的最重要的部分了。
设置按钮监听事件，通过获取按钮的信息来进行判断运算。
在我们进行加减乘除计算的时候会出现一个特殊情况，除数为0，所以我们要预防出现异常影响程序的运行，我们就要进行异常的捕获处理，这里我是自定义了一个异常类munber_Exception，然后我们利用try｛｝catch｛｝语句来进行异常捕获和处理。
public double division(double x,double y)throws munber_Exception{if(y==0){throw new munber_Exception("除数不能为0！");}else{return x/y;}}@Overridepublic void actionPerformed(ActionEvent e) {try { String act=e.getActionCommand();//这个方法返回的是事件源组件的“命令” ， 这个“命令” 实际上就是事件源组件上的“Label（标签）字符串”，即如果我按了“9”这个按钮他就会返回一个“9的值”char a=act.charAt(0);//取act这个字符串的首字符if (a=='0' ||a=='1' || a=='2' ||a=='3'||a=='4'||a=='5'||a=='6'||a=='7'||a=='8'||a=='9'||a=='.') {if(oper=='~'){//当oper=='~'时，则操作符为空strA.append(a);show.setText(String.valueOf(strA));}else {strB.append(a);show.setText(String.valueOf(strA)+oper+String.valueOf(strB));}}else if(a=='+'||a=='-'||a=='/'||a=='*'||a=='%'){oper=a;show.setText(String.valueOf(strA)+oper);}else if(a=='='){ A = Double.parseDouble(String.valueOf(strA)); B = Double.parseDouble(String.valueOf(strB)); double j;int len1=strA.length();int len2=strB.length(); if (oper == '+') { j = A + B; show.setText(Double.toString(j)); strA.delete(0,len1); strB.delete(0,len2); strA.append(j); } else if (oper == '-') { j = A - B; show.setText(Double.toString(j)); strA.delete(0,len1); strB.delete(0,len2); strA.append(j); } else if (oper == '*') { j = A * B; show.setText(Double.toString(j)); strA.delete(0,len1); strB.delete(0,len2); strA.append(j); } else if (oper == '/') { try{j= division(A, B);}catch(munber_Exception u){ show.setText(u.shows()); } } else if (oper == '%') { j = A % B; show.setText(Double.toString(j)); strA.delete(0,len1); strB.delete(0,len2); strA.append(j); }} else if (a=='C') {//清除show.setText(" ");oper='~';int len1=strA.length();int len2=strB.length();strA.delete(0,len1);strB.delete(0,len2);} else if (a=='D'){//删除 if(oper!='~'){ if(strB.length()>0){ strB.delete(strB.length()-1,strB.length()); show.setText(String.valueOf(strA)+oper+String.valueOf(strB)); } else show.setText("0"); }if(oper=='~'){ if(strA.length()>0){ strA.delete(strA.length()-1,strA.length()); show.setText(String.valueOf(strA)); }}} }catch(ArithmeticException m){System.out.println("除数不能为0");}}完整代码如下：
class munber_Exceptionextends Exception{//异常处理String e;public munber_Exception(){}public munber_Exception(String message){this.e=message;}public String shows(){return e;}}class cal extends JFrame implements ActionListener {private JPanel p1, p2;private JTextArea show;private String box ;JMenuBar menubar;JMenu menu1, menu2, menu3;StringBuffer strA;StringBuffer strB;char oper ='~';doubleA;doubleB;private String[] text2 = {"C", "CE","%", "/","7", "8", "9", "*","4", "5", "6", "-","1", "2", "3", "+","DEL","0", ".", "="};//计算器按钮面板private JButton[] munButton = new JButton[text2.length];public cal() {p1 = new JPanel();p2 = new JPanel();show = new JTextArea();p1.setSize(600, 100);menubar = new JMenuBar();menu1 = new JMenu("查看(V)");menu2 = new JMenu("编辑(E)");menu3 = new JMenu("帮助(H)");strB=new StringBuffer();strA=new StringBuffer();}public void init() {//初始化this.setTitle("计算器");this.setBounds(200, 200, 320, 300);this.setLayout(new BorderLayout());this.add(p1, BorderLayout.CENTER);this.add(p2, BorderLayout.SOUTH);menubar.add(menu1);menubar.add(menu2);menubar.add(menu3);this.setJMenuBar(menubar);this.setLocationRelativeTo(null);this.setResizable(false);show.setPreferredSize(new Dimension(300, 100));p1.add(show);p2.setLayout(new GridLayout(5, 4, 2, 3));//添加数字按键for (int i = 0; i < text2.length; i++) {munButton[i] = new JButton(text2[i] + " ");p2.add(munButton[i]);}for (int i = 0; i 0){ strB.delete(strB.length()-1,strB.length()); show.setText(String.valueOf(strA)+oper+String.valueOf(strB)); } else show.setText("0"); }if(oper=='~'){ if(strA.length()>0){ strA.delete(strA.length()-1,strA.length()); show.setText(String.valueOf(strA)); }}} }catch(ArithmeticException m){System.out.println("除数不能为0");}}}public class Calculator {//调用public static void main(String[] args) {cal Calculator1 = new cal();Calculator1.init();}}