Java实现简单计算器的探索性做法

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;


public class calculator extends JFrame {
   //设置按钮，包括运算数字和运算符号 
   JButton b0 = new JButton("0");
   JButton b1 = new JButton("1");
   JButton b2 = new JButton("2");
   JButton b3 = new JButton("3");
   JButton b4 = new JButton("4");
   JButton b5 = new JButton("5");
   JButton b6 = new JButton("6");
   JButton b7 = new JButton("7");
   JButton b8 = new JButton("8");
   JButton b9 = new JButton("9");
   JButton jiaButton = new JButton("+");//加
   JButton jianButton = new JButton("-");//减
   JButton chengButton = new JButton("*");//乘
   JButton chuButton = new JButton("/");//除
   JButton yuButton = new JButton("%");//求余
   JButton jjButton = new JButton("+/-");//正负
   JButton sqrtButton = new JButton("sqrt");//求根
   JButton dianButton = new JButton(".");//小数点
   JButton dengButton = new JButton("=");//等号
   JButton daoButton = new JButton("1/x");//求1/输入数
   JButton backButton = new JButton("Backpace");//回退
   JButton cButton = new JButton("C");//清除
   public double op1;
   public double op2;
   public static final int JIA = 0;
   public static final int JIAN = 1;
   public static final int CHENG = 2;
   public static final int CHU = 3;
   public static final int YU = 4;
   public int currentop = 0;
   private boolean opEnd = false;
   //创建面板并进行基本设置
   JPanel panel1 = new JPanel();
   JPanel panel2 = new JPanel();
   JPanel panel3 = new JPanel();
   JPanel panel4 = new JPanel();
   JTextField result = new JTextField(20);
   public calculator() {
      initPanel2();
      initPanel3();
      panel2.setLayout(new GridLayout(5, 4)); //设置总面板边框
      panel1.setLayout(new BorderLayout(0,0));
      panel1.add(panel3, BorderLayout.NORTH);// 设置位置
      panel1.add(panel2, BorderLayout.CENTER);// 设置位置
      getContentPane().add(panel1);
      addActionListeners();//按钮监听器
      setSize(600,400);//窗体大小
      setLocation(500, 300);//窗体位置
      setVisible(true);//窗体显示
      setDefaultCloseOperation(calculator.EXIT_ON_CLOSE);//窗体关闭
      this.setResizable(false);
      this.setTitle("计算器");
   }


   private void initPanel2() {
      // 把组件添加相应panel上
      panel2.add(b7);
      panel2.add(b8);
      panel2.add(b9);
      panel2.add(chuButton);
      panel2.add(b4);
      panel2.add(b5);
      panel2.add(b6);
      panel2.add(chengButton);
      panel2.add(b1);
      panel2.add(b2);
      panel2.add(b3);
      panel2.add(jianButton);
      panel2.add(b0);
      panel2.add(jjButton);
      panel2.add(dianButton);
      panel2.add(jiaButton);
      panel2.add(daoButton);
      panel2.add(yuButton);
      panel2.add(sqrtButton);
      panel2.add(dengButton);
   }
   private void addActionListeners() {
      ActionHandler c = new ActionHandler();
      //按钮监听
      b0.addActionListener(c);
      b1.addActionListener(c);
      b2.addActionListener(c);
      b3.addActionListener(c);
      b4.addActionListener(c);
      b5.addActionListener(c);
      b6.addActionListener(c);
      b7.addActionListener(c);
      b8.addActionListener(c);
      b9.addActionListener(c);
      jiaButton.addActionListener(c);
      dengButton.addActionListener(c);
      chengButton.addActionListener(c);
      chuButton.addActionListener(c);
      jianButton.addActionListener(c);
      jjButton.addActionListener(c);
      dianButton.addActionListener(c);
      sqrtButton.addActionListener(c);
      yuButton.addActionListener(c);
      daoButton.addActionListener(c);
      backButton.addActionListener(c);
      cButton.addActionListener(c);
   }
   private void initPanel3() {
      //输入和结果显示
      panel3.setLayout(new GridLayout(2, 1));
      panel3.add(result);
      panel3.add(panel4);
      panel3.setPreferredSize(new Dimension(100,100));
      //清除和回退
      panel4.setLayout(new GridLayout(1, 2));
      panel4.add(backButton);
      panel4.add(cButton);
   }
//运算类
class ActionHandler implements ActionListener {
   public void actionPerformed(ActionEvent e) {
      //输入数字
      if (e.getSource() == b0) {
         if (opEnd == false) {
            result.setText("");
         }
         result.setText(result.getText() + "0");
      }
      if (e.getSource() == b1) {
         if (opEnd == false) {
            result.setText("");
         }
         result.setText(result.getText() + "1");
         opEnd = true;
      }
      if (e.getSource() == b2) {
         if (opEnd == false) {
            result.setText("");
         }
         result.setText(result.getText() + "2");
         opEnd = true;
      }
      if (e.getSource() == b3) {
         if (opEnd == false) {
            result.setText("");
         }
         result.setText(result.getText() + "3");
         opEnd = true;
      }
      if (e.getSource() == b4) {
         if (opEnd == false) {
            result.setText("");
         }
         result.setText(result.getText() + "4");
         opEnd = true;
      }
      if (e.getSource() == b5) {
         if (opEnd == false) {
            result.setText("");
            }
         result.setText(result.getText() + "5");
         opEnd = true;
      }
      if (e.getSource() == b6) {
         if (opEnd == false) {
            result.setText("");
         }
         result.setText(result.getText() + "6");
         opEnd = true;
      }
      if (e.getSource() == b7) {
         if (opEnd == false) {
            result.setText("");
         }
         result.setText(result.getText() + "7");
         opEnd = true;
      }
      if (e.getSource() == b8) {
         if (opEnd == false) {
            result.setText("");
         }
         result.setText(result.getText() + "8");
         opEnd = true;
      }
      if (e.getSource() == b9) {
         if (opEnd == false) {
            result.setText("");
         }
         result.setText(result.getText() + "9");
         opEnd = true;
      }
      try {
         if (e.getSource() == jiaButton) {//点击+按钮，下同
            op1 = Double.parseDouble(result.getText());
            //说明操作数已经输入完毕
            opEnd = false;
            currentop = JIA;
         }
         if (e.getSource() == chengButton) {//乘
            op1 = Double.parseDouble(result.getText());
            //说明操作数已经输入完毕
            opEnd = false;
            currentop = CHENG;
         }
         if (e.getSource() == chuButton) {//除
            op1 = Double.parseDouble(result.getText());
            //说明操作数已经输入完毕
            opEnd = false;
            currentop = CHU;
         }
         if (e.getSource() == jianButton) {//减
            op1 = Double.parseDouble(result.getText());
            //说明操作数已经输入完毕
            opEnd = false;
            currentop = JIAN;
         }
         if (e.getSource() == yuButton) {//余
            op1 = Double.parseDouble(result.getText());
            //说明操作数已经输入完毕
            opEnd = false;
            currentop = YU;
         }
         if (e.getSource() == jjButton) {//正负
            String tmp = result.getText();
            if (tmp.equals("") || tmp.equals("0")) {
               return;
            }
            if (tmp.charAt(0) == ‘-‘) {
               tmp = tmp.substring(1);
            } else {
               tmp = ‘-‘ + tmp;
            }
            result.setText(tmp);
         }
         if (e.getSource() == dianButton) {//小数点
            String tmp = result.getText();
            if (tmp.equals("")) {
               return;
            }
            if (tmp.indexOf(".") != -1) {
               return;
            }
            tmp = tmp + ".";
            result.setText(tmp);
         }
         if(e.getSource() == daoButton) {//1/x
            String tmp = result.getText();
            if (tmp.equals(" ")) {
               return;
            }
            double d; // 先定义d
            d = Double.parseDouble(tmp);
            if(d==0) {
               result.setText("被除数不能为零");
               return;
            }
            op2 = 1/d;
            result.setText(op2 + "");
         }
         if (e.getSource() == sqrtButton) {//求根
            String tmp = result.getText();
            if (tmp.equals(" ")) {
               return;
            }
            double d;
            d = Double.parseDouble(tmp);
            if (d < 0) {
               result.setText("不能对负数求平方根");
               return;
            }
            op2 = Math.sqrt(d);
            result.setText(op2 + "");
         }
         if (e.getSource() == backButton) {//回退
            String s = result.getText();
            result.setText("");
            for (int i = 0; i < s.length() - 1; i++) {
               char a = s.charAt(i);
               result.setText(result.getText() + a);
            }
         }
         if (e.getSource() == cButton) {//清除
            result.setText("0");
            opEnd = false;
         }
         if (e.getSource() == dengButton) { //点击“=”按钮
            op2 = Double.parseDouble(result.getText());
            switch (currentop) {
            case JIA:
               result.setText(op1 + op2 + "");
               break;
            case JIAN:
               result.setText(op1 - op2 + "");
               break;
            case CHENG:
               result.setText(op1 * op2 + "");
               break;
            case CHU:
               if (op2 == 0) {
                  result.setText("0不能为除数");
                  break;
               }
               result.setText(op1 / op2 + "");
               break;
            case YU:
               if (op2 == 0) {
                  result.setText("0不能为除数");
                  break;
               }
               result.setText(op1 % op2 + "");
               break;
            }
            opEnd = false;
         }
      } catch (Exception e1) {
         result.setText("输入有误，请重新输入");
         opEnd = false;
      }
      }
   }
   public static void main(String[] args) {
      new calculator();// 生成类实例
   }