// Calculator.java
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.math.BigDecimal;
public class Calculator extends  implements 
{
   private boolean ifAction;
   private double ansPre;
   private  ansStr = "";
   private int sign = 0; // 1: + 2: - 3: x 4: /
   private boolean ifDot = true;
   private  textField;
   private  fnt = new ("Monospace", .PLAIN, 26);
   private  ButtonPanel = new ();
   private  TextPanel = new ();
   private []  = new [20];
   private  mb = new ();
   private  fileMenu = new ("文件");
   private  aboutMenu = new ("关于");
   private [] filem = {new ("退出")};
   private [] aboutm = {new ("关于作者")};
    name[] = {"Bksp", "CE", "Clr", "+/-",
               " 7 ", " 8 ", " 9 ", " / ",
              " 4 ", " 5 ", " 6 ", " x ",
               " 1 ", " 2 ", " 3 ", " - ",
               " 0 ", " . ", " = ", " + "};
   public Calculator() {
        super("计算器");
        fileMenu.add(filem[0]);
        aboutMenu.add(aboutm[0]);
    filem[0].addActionListener(this);
    aboutm[0].addActionListener(this);
    mb.add(fileMenu);
    mb.add(aboutMenu);
    setJMenuBar(mb);
    textField = new (15);
    textField.setText("0");
    textField.setEditable(false);
    textField.setFont(fnt);
    textField.setBackground(.white);
    textField.setHorizontalAlignment(.RIGHT);
    TextPanel.add(textField);
    for (int i = 0; i < name.length; i++) {
         [i] = new (name[i]);
         [i].addActionListener(this);
    }
    setLayout(new (10, 10));
    add(TextPanel, .NORTH);
    TextPanel.setBorder(.createEmptyBorder(20,10,10,10));
    for (int i = 0; i < name.length; i++) {
         ButtonPanel.add([i]);
    }
    ButtonPanel.setBorder(.createEmptyBorder(0,10,30,10));
    add(ButtonPanel, .CENTER);
    ButtonPanel.setLayout(new (5, 4, 10, 10));
 }
 public void initAll() {
    ansStr = "";
    sign = 0;
    ifDot = true;
    ifAction = false;
    refresh();
 }
 public void init() {
    ansStr = "";
    ifDot = true;
    refresh();
 }
 public void refresh() {
    if (ansStr.length() == 0) {
          textField.setText("0");
    } else {
          textField.setText(ansStr);
    }
 }
 public void cal() {
    if (sign == 1) {
          ansPre = ansPre + .parseDouble(ansStr);
    } else if (sign == 2) {
          ansPre = ansPre - .parseDouble(ansStr);
    } else if (sign == 3) {
          ansPre = ansPre * .parseDouble(ansStr);
    } else if (sign == 4) {
          ansPre = ansPre / .parseDouble(ansStr);
    }
     bd = new (ansPre);
    bd=bd.setScale(13, .ROUND_HALF_UP);
    ansPre = bd.doubleValue();
    if (sign != 0) {
          if ((ansPre - (int)ansPre == 0)) {
                ansStr = "" + (int)ansPre;
          } else {
                ansStr = "" + ansPre;
          }
    }
    sign = 0;
 }
 
 public void actionPerformed ( e) {
     B = e.getActionCommand();
    if (B.charAt(1) == '0' && (ansStr.length() < 15 || ifAction)) {
          if (ifAction) {
                init();
                ifAction = false;
          }
          if (!(ansStr.length() == 1 && ansStr.charAt(0) == '0')) {
                ansStr = ansStr + B.charAt(1);
          }
     } else if ((B.charAt(1) >= '1' && B.charAt(1) <= '9')
            && (ansStr.length() < 15 || ifAction)) {
          if (ifAction) {
                init();
                ifAction = false;
          }
          if (ansStr.length() == 1 && ansStr.charAt(0) == '0') {
                ansStr = "" + B.charAt(1);
          } else {
                ansStr = ansStr + B.charAt(1);
          }
     } else if (B.charAt(0) == 'B' && ansStr.length() > 0) {
         int len = ansStr.length();
         if (ansStr.charAt(len - 1) == '.') {
               ifDot = true;
         }
         ansStr = ansStr.substring(0, len - 1);
    } else if (B.charAt(0) == '+') {
         if (ansStr.charAt(0) == '-') {
               int len = ansStr.length();
               ansStr = ansStr.substring(1, len);
         } else if (ansStr.length() > 0){
               ansStr = '-' + ansStr;
         }
    } else if (B.charAt(1) == '.' && ifDot) {
         ansStr = ansStr + B.charAt(1);
         ifDot = false;
    } else if (B.charAt(1) == 'l') {
         initAll();
    } else if (B.charAt(1) == 'E') {
         init();
    } else if (B.charAt(1) == '+') {
         if (!ifAction) {
               if (sign != 0) {
                     cal();
               }
               ansPre = .parseDouble(ansStr);
         }
         sign = 1;
         ifAction = true;
    } else if (B.charAt(1) == '-') {
         if (!ifAction) {
               if (sign != 0) {
                     cal();
               }
               ansPre = .parseDouble(ansStr);
         }
         sign = 2;
         ifAction = true;
    }else if (B.charAt(1) == 'x') {
         if (!ifAction) {
               if (sign != 0) {
                     cal();
               }
               ansPre = .parseDouble(ansStr);
         }
         sign = 3;
         ifAction = true;
    }else if (B.charAt(1) == '/') {
         if (!ifAction) {
               if (sign != 0) {
                     cal();
                 }
                 ansPre = .parseDouble(ansStr);
            }
            sign = 4;
            ifAction = true;
       } else if (B.charAt(1) == '=') {
            cal();
            ifAction = true;
            sign = 0;
       } else if (B.compareTo("退出") == 0) {
            .exit(0);
       } else if (B.compareTo("关于作者") == 0) {
            .showMessageDialog(null, " 作者:CoderMAX\n 专业:软件工
程\n Blog: www.codermax.com", "关于作者", .PLAIN_MESSAGE);
       }
       refresh();
   }
   public static void main([] args) {
       Calculator frame = new Calculator();
       frame.setTitle("计算器 By CoderMAX");
       frame.setSize(390, 370);
       frame.setVisible(true);
       frame.setResizable(false);
       frame.setDefaultCloseOperation(.EXIT_ON_CLOSE);
   }
}