简易计算器第一版

public class Main {
  public static void main(String[] args) {
    MyFrame frame= new MyFrame("曙光一号");
    frame.setVisible(true);
  }
}

界面如下图：

import java.awt.Color;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.math.BigDecimal;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class MyFrame extends JFrame implements ActionListener {
  private static final long serialVersionUID = 1L;

  // 设定最大长度！！！考虑负数！！！单目运算符多次操作！！！
  // .....
  String string_1 = "";// 第一个数
  String string_2 = "";// 符号
  String string_3 = "";// 第二个数
  String strings = "0";// 用来设置label(为string_1+string_2+string_3)
  boolean isNum_1Exist = false;// 第一个数是否存在
  boolean isNum_2Exist = false;// 第二个数是否存在
  boolean isSignExist = false;// 是否有运算符
  boolean isNum_1Point = false;// 第一个数是否有小数点
  boolean isNum_2Point = false;// 第二个数是否有小数点
  boolean isAlong = false;//单目运算
  JLabel label = new JLabel();

  JButton[] buttons = new JButton[20];

  public MyFrame(String string) {
    super(string);
    setBounds(450, 80, 300, 400);// 设置窗口位置大小
    setResizable(false);// 窗口不可变
    setDefaultCloseOperation(EXIT_ON_CLOSE);// 关闭操作，直接关闭
    setLayout(new GridLayout(6, 1));
    Font font = new Font(getName(), Font.BOLD, 35);

    /// 面板1/
    JPanel panel_1 = new JPanel();
    label.setHorizontalAlignment(JLabel.RIGHT);
    label.setFont(new Font("楷体", ALLBITS, 15));
    panel_1.add(label);
    add(panel_1);

    /// 面板2/
    JPanel panel_2 = new JPanel();
    panel_2.setLayout(new GridLayout(1, 4));
    panel_2.setBackground(Color.lightGray);
    panel_2.setFont(font);
    buttons[0] = new JButton("%");
    buttons[1] = new JButton("sqrt");
    buttons[2] = new JButton("^2");
    buttons[3] = new JButton("AC");
    for (int i = 0; i < 4; i++) {
      panel_2.add(buttons[i]);
    }
    add(panel_2);
    /// 面板3/
    JPanel panel_3 = new JPanel();
    panel_3.setLayout(new GridLayout(1, 4));
    panel_3.setBackground(Color.lightGray);
    panel_3.setFont(font);
    buttons[4] = new JButton("7");
    buttons[5] = new JButton("8");
    buttons[6] = new JButton("9");
    buttons[7] = new JButton("+");
    for (int i = 4; i < 8; i++) {
      panel_3.add(buttons[i]);
    }
    add(panel_3);

    /// 面板4/
    JPanel panel_4 = new JPanel();
    panel_4.setLayout(new GridLayout(1, 4));
    panel_4.setBackground(Color.lightGray);
    panel_4.setFont(font);
    buttons[8] = new JButton("4");
    buttons[9] = new JButton("5");
    buttons[10] = new JButton("6");
    buttons[11] = new JButton("-");

    for (int i = 8; i < 12; i++) {
      panel_4.add(buttons[i]);
    }
    add(panel_4);

    /// 面板5/
    JPanel panel_5 = new JPanel();
    panel_5.setLayout(new GridLayout(1, 4));
    panel_5.setBackground(Color.lightGray);
    panel_5.setFont(font);
    buttons[12] = new JButton("1");
    buttons[13] = new JButton("2");
    buttons[14] = new JButton("3");
    buttons[15] = new JButton("*");

    for (int i = 12; i < 16; i++) {
      panel_5.add(buttons[i]);
    }
    add(panel_5);
    /// 面板6/
    JPanel panel_6 = new JPanel();
    panel_6.setLayout(new GridLayout(1, 4));
    panel_6.setBackground(Color.lightGray);
    panel_6.setFont(font);
    buttons[16] = new JButton("0");
    buttons[17] = new JButton(".");
    buttons[18] = new JButton("=");
    buttons[19] = new JButton("/");

    for (int i = 16; i < 20; i++) {
      panel_6.add(buttons[i]);
    }
    add(panel_6);
    // 添加监听
    for (int i = 0; i < buttons.length; i++) {
      buttons[i].addActionListener(this);
    }
  }

  @Override
  public void actionPerformed(ActionEvent e) {
    if (e.getSource() == buttons[3]) {// AC
      remove();
    }

     符号/
    if (isNum_1Exist) {
      // 单目运算不需要按等号
      if (e.getSource() == buttons[1] && isNum_1Exist) {// sqrt
        double i = Double.parseDouble(string_1);
        double s = Math.sqrt(i);
        String string = "" + s;
        label.setText(string);
        string_1 = string;
        isNum_1Exist = true;
        isAlong = true;
      } else if (e.getSource() == buttons[2] && isNum_1Exist) {// ^2
        double i = Double.parseDouble(string_1);
        i = i * i;
        String string = "" + i;
        label.setText(string);
        string_1 = string;
        isNum_1Exist = true;
        isAlong = true;
      } else if (e.getSource() == buttons[0]) {// %
        setDual("%");
      } else if (e.getSource() == buttons[7]) {// +
        setDual("+");
      } else if (e.getSource() == buttons[11]) {// -
        setDual("-");
      } else if (e.getSource() == buttons[15]) {// *
        setDual("*");
      } else if (e.getSource() == buttons[19]) {// /
        setDual("/");
      } else if (e.getSource() == buttons[18]) {// =
        // 计算：
        String str = count();
        // 清空数据
        remove();
        label.setText(str);
      }
    }
    /// 数字//

    // 第一个数没有 或者 有了第一个数还没有符号 就加到第一个数
    if (e.getSource() == buttons[4]) {// 7
      setNum("7");
    } else if (e.getSource() == buttons[5]) {// 8
      setNum("8");
    } else if (e.getSource() == buttons[6]) {// 9
      setNum("9");
    } else if (e.getSource() == buttons[8]) {// 4
      setNum("4");
    } else if (e.getSource() == buttons[9]) {// 5
      setNum("5");
    } else if (e.getSource() == buttons[10]) {// 6
      setNum("6");
    } else if (e.getSource() == buttons[12]) {// 1
      setNum("1");
    } else if (e.getSource() == buttons[13]) {// 2
      setNum("2");
    } else if (e.getSource() == buttons[14]) {// 3
      setNum("3");
    } else if (e.getSource() == buttons[16]) {// 0
      setNum("0");
    } else if (e.getSource() == buttons[17]) {// .
      // 一个数只能有一个
      if ((!isNum_1Exist) || (isNum_1Exist && !isSignExist)) {// 1
        if (!isNum_1Point) {
          setNum1(".");
          isNum_1Point = true;
        }
      } else {// 2
        if (!isNum_2Point)
          setNum2(".");
        isNum_2Point = true;
      }
    }
  }

  // 计算(双目)
  // 结果的label 在这里统一设置
  private String count() {
    try {
      BigDecimal b1 = new BigDecimal(string_1);
      BigDecimal b2 = new BigDecimal(string_3);
      switch (string_2) {
      case "+":
        BigDecimal b = b1.add(b2);
        strings = b.toString();
        break;
      case "-":
        b = b1.subtract(b2);
        strings = b.toString();
        break;
      case "*":
        b = b1.multiply(b2);
        strings = b.toString();
        break;
      case "/":
        if (!(string_3.equals("0"))) {
          b = b1.divide(b2);
          strings = b.toString();
        }else {
          strings = "除数不能为零";
        }
        break;
      case "%":
        b = b1.remainder(b2);
        strings = b.toString();
        break;
      default:

      }
    } catch (Exception e) {
    }
    return strings;
  }

  private void setDual(String s) {
    // 双目运算：第一个数存在，第二个数还不存在的是时候可以加符号
    // 否则如果两个都存在了就相当于等号(执行运算方法！！)
    if (isNum_1Exist && !isNum_2Exist) {
      string_2 = s;
      isSignExist = true;
      strings = string_1 + string_2;
      label.setText(strings);
    } else if (isNum_1Exist && isNum_2Exist) {
      String str = count();
      remove();
      string_1 = str;
      isNum_1Exist = true;
      string_2 = s;
      isSignExist = true;
      strings = string_1 + string_2;
      label.setText(strings);
    }
  }

  private void remove() {
    label.setText("");
    isNum_1Exist = false;
    isNum_2Exist = false;
    isSignExist = false;
    isNum_1Point = false;
    isNum_2Point = false;
    string_1 = "";
    string_2 = "";
    string_3 = "";
  }

  private void setNum(String s) {
    if(isAlong){
      string_1 = "";
      isNum_1Exist = false;
      isAlong = false;
    }
    if ((!isNum_1Exist) || (isNum_1Exist && !isSignExist)) {// 1
      setNum1(s);
    } else {// 2
      setNum2(s);
    }
  }

  private void setNum1(String s) {
    string_1 += s;
    isNum_1Exist = true;
    label.setText(string_1);
  }

  private void setNum2(String s) {
    string_3 += s;
    isNum_2Exist = true;
    strings = string_1 + string_2 + string_3;
    label.setText(strings);
  }
}