textAnswer.setText("");
          prekey = key = 2;
        }
        //'/'操作
        if (temp == buttonDiv) {
          switch (prekey) {
            case 0:
              answerd += Double.parseDouble(textAnswer.getText());
              break;
            case 1:
              answerd -= Double.parseDouble(textAnswer.getText());
              break;
            case 2:
              answerd *= Double.parseDouble(textAnswer.getText());
              break;
            case 3:
              if (Double.parseDouble(textAnswer.getText()) == 0) {
                textAnswer.setText("除數不能為零");
                clickable = false;
              }
              else
                answerd /= Double.parseDouble(textAnswer.getText());
              break;
            default:
              answerd = Double.parseDouble(textAnswer.getText());
          }
          textAnswer.setText("");
          prekey = key = 3;
        }
      }
      //'='操作
      if (temp == buttonEqual && clickable == true) {
        //如果連續按'=',則進行連續運算
        if (prekey == 5) {
          if (key == 0) {
            answerd += vard;
            textAnswer.setText(df.format(answerd));
          }
          if (key == 1) {
            answerd -= vard;
            textAnswer.setText(df.format(answerd));
          }
          if (key == 2) {
            answerd *= vard;
            textAnswer.setText(df.format(answerd));
          }
          if (key == 3) {
            if (Double.parseDouble(textAnswer.getText()) == 0) {
              textAnswer.setText("除數不能為零");
              clickable = false;
            }
            else {
              answerd /= vard;
              textAnswer.setText(df.format(answerd));
            }
          }
        }
        else {
          vard = Double.parseDouble(textAnswer.getText());
          if (key == 0) {
            prekey = -1;
            answerd += Double.parseDouble(textAnswer.getText());
            textAnswer.setText(df.format(answerd));
          }
          if (key == 1) {
            prekey = -1;
            answerd -= Double.parseDouble(textAnswer.getText());
            textAnswer.setText(df.format(answerd));
          }
          if (key == 2) {
            prekey = -1;
            answerd *= Double.parseDouble(textAnswer.getText());
            textAnswer.setText(df.format(answerd));
          }
          if (key == 3) {
            prekey = -1;
            if (Double.parseDouble(textAnswer.getText()) == 0) {
              textAnswer.setText("除數不能為零");
              clickable = false;
            }
            else {
              answerd /= Double.parseDouble(textAnswer.getText());
              textAnswer.setText(df.format(answerd));
            }
          }
        }
        prekey = 5;
      }
      //'%'操作，對第二個操作數除以100
      if (temp == buttonMod && clickable == true) {
        if (answerd == 0) {
          String s = textAnswer.getText();
          textAnswer.setText(s);
        }
        else {
          boolean isDot = false;
          for (int i = 0; i < textAnswer.getText().length(); i++)
            if ('.' == textAnswer.getText().charAt(i)) {
              isDot = true;
              break;
            }
          //如果是double數，除100
          if (isDot == true) {
            double dtemp = Double.parseDouble(textAnswer.getText());
            dtemp = dtemp / 100.0;
            textAnswer.setText(Double.toString(dtemp));
          }
          else {
            //如果是int數但能被100整除，則去掉末尾兩個零
            if (Integer.parseInt(textAnswer.getText()) % 100 == 0) {
              int itemp = Integer.parseInt(textAnswer.getText());
              itemp /= 100;
              textAnswer.setText(Integer.toString(itemp));
            }
            //如果是int數，但不能被100整除，則按double數處理
            else {
              double dtemp = Double.parseDouble(textAnswer.getText());
              dtemp = dtemp / 100.0;
              textAnswer.setText(Double.toString(dtemp));
            }
          }
        }
      }
      //開根號運算
      if (temp == buttonSqrt && clickable == true) {
        String s = textAnswer.getText();
        if (s.charAt(0) == '-') {
          textAnswer.setText("負數不能開根號");
          clickable = false;
        }
        else
          textAnswer.setText(Double.toString(java.lang.Math.sqrt(Double.
              parseDouble(textAnswer.getText()))));
      }
      //倒數運算
      if (temp == buttonDao && clickable == true) {
        if (textAnswer.getText().charAt(0) == '0' &&
            textAnswer.getText().length() == 1) {
          textAnswer.setText("零不能求倒數");
          clickable = false;
        }
        else {
          boolean isDec = true;
          int i, j, k;
          String s = Double.toString(1 / Double.parseDouble(textAnswer.getText()));
          for (i = 0; i < s.length(); i++)
            if (s.charAt(i) == '.')
              break;
          for (j = i + 1; j < s.length(); j++)
            if (s.charAt(j) != '0') {
              isDec = false;
              break;
            }
          if (isDec == true) {
            String stemp = "";
            for (k = 0; k < i; k++)
              stemp += s.charAt(k);
            textAnswer.setText(stemp);
          }
          else
            textAnswer.setText(s);
        }
      }
      //按下'+/-'按鈕時處理
      if (temp == buttonAddAndSub && clickable == true) {
        boolean isNumber = true;
        String s = textAnswer.getText();
        for (int i = 0; i < s.length(); i++)
          if (! (s.charAt(i) >= '0' && s.charAt(i) <= '9' || s.charAt(i) == '.' ||
                 s.charAt(i) == '-')) {
            isNumber = false;
            break;
          }
        if (isNumber == true) {
          //如果當前字符串首字母有'-'號,代表現在是個負數,再按下時,則將首符號去掉
          if (s.charAt(0) == '-') {
            textAnswer.setText("");
            for (int i = 1; i < s.length(); i++) {
              char a = s.charAt(i);
              textAnswer.setText(textAnswer.getText() + a);
            }
          }
          //如果當前字符串第一個字符不是符號，則添加一個符號在首字母處
          else
            textAnswer.setText('-' + s);
        }
      }
      //計算器有關內存操作
      //'MC'的操作，將內存清0
      if (temp == buttonMC && clickable == true) {
        memoryd = memoryi = 0;
        textMemory.setText("");
      }
      //'MS'的操作，將當前文本框內容保存入內存，顯示'M'
      if (temp == buttonMS && clickable == true) {
        boolean isDot = false;
        textMemory.setText("   M");
        for (int i = 0; i < textAnswer.getText().length(); i++)
          if ('.' == textAnswer.getText().charAt(i)) {
            isDot = true;
            break;
          }
        //如果是double,則存入memoryd(double存儲器)
        if (isDot == true) {
          memoryd = Double.parseDouble(textAnswer.getText());
          memoryi = 0; //保證存儲器中存放最新的值
        }
        //如果是int,則存入memoryi(int存儲器)
        else {
          memoryi = Integer.parseInt(textAnswer.getText());
          memoryd = 0; //保證存儲器中存放最新的值
        }
      }
      //'MR'的操作，將存儲器中的信息輸出
      if (temp == buttonMR && clickable == true) {
        if (memoryd != 0)
          textAnswer.setText(Double.toString(memoryd));
        if (memoryi != 0)
          textAnswer.setText(Integer.toString(memoryi));
      }
      //'M+'的功能，將當前文本框里的數據和存儲器中數據相加后，再存入存儲器
      if (temp == buttonMAdd && clickable == true) {
        boolean isDot = false;
        for (int i = 0; i < textAnswer.getText().length(); i++)
          if ('.' == textAnswer.getText().charAt(i)) {
            isDot = true;
            break;
          }
        if (memoryi != 0) { //存儲中是一個int型數
          if (isDot == false) //被加數是一個int型數
            memoryi += Integer.parseInt(textAnswer.getText());
          else { //被加數是一個double型數，則將int存儲器中數傳入double存儲器與當前數相加，int存儲器清零
            memoryd = memoryi + Double.parseDouble(textAnswer.getText());
            memoryi = 0;
          }
        }
        else
          memoryd += Double.parseDouble(textAnswer.getText());
      }
      //按下'Backspace'鍵，利用循環將當前字符串中的最后一個字母刪除
      if (temp == buttonBk && clickable == true) {
        String s = textAnswer.getText();
        textAnswer.setText("");
        for (int i = 0; i < s.length() - 1; i++) {
          char a = s.charAt(i);
          textAnswer.setText(textAnswer.getText() + a);
        }
      }
      //按下'CE'按鈕，將當前文本框內數據清除
      if (temp == buttonCe) {
        textAnswer.setText("");
        clickable = true;
      }
      //按下'C'按鈕，文本框內數據清除，同時var,answer清0
      if (temp == buttonC) {
        vard = answerd = 0;
        textAnswer.setText("");
        clickable = true;
      }
      //按下'復制'菜單欄
      if (temp == copyItem) {
        copy = textAnswer.getText();
      }
      //按下'粘貼'菜單欄
      if (temp == pasteItem) {
        textAnswer.setText(copy);
      }
      if (temp == sItem) {
        JOptionPane.showMessageDialog(panel, "當前是標準型計算器，\n科學型計算器有待更新。");
      }
      //按下'幫助主題'菜單欄
      if (temp == topHelp) {
        JOptionPane.showMessageDialog(panel, scrollHelp);
      }
      //按下'數字分組'菜單欄
      if (temp == numberGroup) {
        if (numberGroup.getText().compareTo("   數字分組(I)") == 0)
          numberGroup.setText("√數字分組(I)");
        else
          numberGroup.setText("   數字分組(I)");
      }
      //按下'關于'菜單欄
      if (temp == aboutCal) {
        JOptionPane.showMessageDialog(panel, "計算器1.00版\n開發者：樓競");
      }
    }
    //輸入中如果有操作非法，比如按下兩次'+'，捕獲異常
    catch (Exception e) {
      textAnswer.setText("操作非法");
      clickable = false;
    }
  }
  //主函數
  public static void main(String args[]) {
    new Calculator();
  }
}