importjava.awt.BorderLayout;importjava.awt.Color;importjava.awt.GridLayout;importjava.awt.event.ActionEvent;importjava.awt.event.ActionListener;importjavax.swing.JButton;importjavax.swing.JFrame;importjavax.swing.JPanel;importjavax.swing.JTextField;/***一个计算器，与Windows附件自带计算器的标准版功能、界面相仿。但还不支持键盘操作。*/publicclassCalculatorextendsJFrameimplementsActionListener{/**计算器上的键的显示名字*/privatefinalString[]KEYS={"7","8","9","/","sqrt","4","5","6","*","%","1","2","3","-","1/x","0","+/-",".","+","="};/**计算器上的功能键的显示名字*/privatefinalString[]COMMAND={"Backspace","CE","C"};/**计算器左边的M的显示名字*/privatefinalString[]M={"","MC","MR","MS","M+"};/**计算器上键的按钮*/privateJButtonkeys[]=newJButton[KEYS.length];/**计算器上的功能键的按钮*/privateJButtoncommands[]=newJButton[COMMAND.length];/**计算器左边的M的按钮*/privateJButtonm[]=newJButton[M.length];/**计算结果文本框*/privateJTextFieldresultText=newJTextField("0");//标志用户按的是否是整个表达式的第一个数字,或者是运算符后的第一个数字privatebooleanfirstDigit=true;//计算的中间结果。privatedoubleresultNum=0.0;//当前运算的运算符privateStringoperator="=";//操作是否合法privatebooleanoperateValidFlag=true;/***构造函数*/publicCalculator(){super();//初始化计算器init();//设置计算器的背景颜色this.setBackground(Color.LIGHT_GRAY);this.setTitle("计算器");//在屏幕(500,300)坐标处显示计算器this.setLocation(500,300);//不许修改计算器的大小this.setResizable(false);//使计算器中各组件大小合适this.pack();}/***初始化计算器*/privatevoidinit(){//文本框中的内容采用右对齐方式resultText.setHorizontalAlignment(JTextField.RIGHT);//不允许修改结果文本框resultText.setEditable(false);//设置文本框背景颜色为白色resultText.setBackground(Color.white);//初始化计算器上键的按钮，将键放在一个画板内JPanelcalckeysPanel=newJPanel();//用网格布局器，4行，5列的网格，网格之间的水平方向间隔为3个象素，垂直方向间隔为3个象素calckeysPanel.setLayout(newGridLayout(4,5,3,3));for(inti=0;i
