package com.itcase_eight;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DateFormat;
import java.util.Date;

/**
 * @author 罗志刚
 * @date 2020/12/16 22:09
 */
public class Calculater {
    public static void createAndShowGUI() {
        Date date=new Date();
        DateFormat format=DateFormat.getDateInstance(DateFormat.SHORT);
        // 对计算器整体框架的建立start
        JFrame f = new JFrame("计算器");// 窗口
        JPanel centerPanel = new JPanel(); // 中间面板
        JPanel startPanel=new JPanel();
        // 初始化功能键
        JButton  left=new JButton("(");
        JLabel  data=new JLabel(format.format(date),JLabel.CENTER);
        data.setFont(new Font("Times New Roman",Font.BOLD,17));
        JButton clear=new JButton("Clear");
        JButton  right=new JButton(")");
        String button[] = { "7", "8", "9", "/", "4", "5", "6", "*", "1", "2", "3", "-", ".", "0", "=", "+"};
        JButton but0 = new JButton(button[0]);
        JButton but1 = new JButton(button[1]);
        JButton but2 = new JButton(button[2]);
        JButton but3 = new JButton(button[3]);
        JButton but4 = new JButton(button[4]);
        JButton but5 = new JButton(button[5]);
        JButton but6 = new JButton(button[6]);
        JButton but7 = new JButton(button[7]);
        JButton but8 = new JButton(button[8]);
        JButton but9 = new JButton(button[9]);
        JButton but10 = new JButton(button[10]);
        JButton but11 = new JButton(button[11]);
        JButton but12 = new JButton(button[12]);
        JButton but13 = new JButton(button[13]);
        JButton but14 = new JButton(button[14]);
        JButton but15 = new JButton(button[15]);
        // 单行输入文本框
        JTextField txt = new JTextField();
        // 使用网格布局方式
        centerPanel.setLayout(new GridLayout(5, 4, 12, 16)); // 左右上下间隔
        centerPanel.add(left);
        centerPanel.add(clear);
        centerPanel.add(right);
        centerPanel.add(data);
        centerPanel.add(but0);
        centerPanel.add(but1);
        centerPanel.add(but2);
        centerPanel.add(but3);
        centerPanel.add(but4);
        centerPanel.add(but5);
        centerPanel.add(but6);
        centerPanel.add(but7);
        centerPanel.add(but8);
        centerPanel.add(but9);
        centerPanel.add(but10);
        centerPanel.add(but11);
        centerPanel.add(but12);
        centerPanel.add(but13);
        centerPanel.add(but14);
        centerPanel.add(but15);
        centerPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        // 设置容器大小
        txt.setPreferredSize(new Dimension(465, 40));
        // 设置字体，风格和字号
        txt.setFont(new Font("宋体", Font.PLAIN, 28));
        f.add(startPanel);
        f.add(txt, BorderLayout.NORTH); // 将单行文本框添加到窗口的 北部
        f.add(centerPanel, BorderLayout.SOUTH); // 将中间面板添加到窗口的南部
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);// 点X关闭窗口
        f.setLocation(400, 200); // 初始化时定位
        f.setSize(500, 300);
        // 展示JFrame窗口
        f.setVisible(true);
        f.setResizable(false); // 禁止拖曳改变窗口大小
        f.pack(); // 让窗口的大小自适应
        // 对计算器整体框架的建立end
        // 为按钮事件添加自定义监听器start
        StringBuffer r=new StringBuffer();
        but0.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("7");
                txt.setText(r.toString());
            }
        });
        but1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("8");
                txt.setText(r.toString());
            }
        });
        but2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("9");
                txt.setText(r.toString());
            }
        });
        but4.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("4");
                txt.setText(r.toString());
            }
        });
        but5.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("5");
                txt.setText(r.toString());
            }
        });
        but6.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("6");
                txt.setText(r.toString());
            }
        });
        left.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("(");
                txt.setText(r.toString());
            }
        });
        right.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append(")");
                txt.setText(r.toString());
            }
        });
        but8.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("1");
                txt.setText(r.toString());
            }
        });
        but9.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("2");
                txt.setText(r.toString());
            }
        });
        but10.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("3");
                txt.setText(r.toString());
            }
        });
        but13.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("0");
                txt.setText(r.toString());
            }
        });
        but15.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("+");
                txt.setText(r.toString());
            }
        });
        but3.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("/");
                txt.setText(r.toString());
            }
        });
        but7.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("*");
                txt.setText(r.toString());
            }
        });
        but12.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append(".");
                txt.setText(r.toString());
            }
        });
        but11.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("-");
                txt.setText(r.toString());
            }
        });
        clear.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.delete(0,r.length());   //清空字符串中的内容
                txt.setText(r.toString());  //将结果显示在文本框中
            }
        });
        but14.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                r.append("=");
                String str=r.toString();
                txt.setText("");
                double result= Computer.solution(str);
                String string=String.valueOf(result);
                r.delete(0,r.length());
                r.append(string);
                txt.setText(string);
            }
        });
    }
    public static void main(String[] args) {
        SwingUtilities.invokeLater(Calculater::createAndShowGUI);
    }
}

package com.itcase_eight;

import java.util.Stack;

/**
 * @author 罗志刚
 * @date 2020/12/16 22:05
 */
public class Computer {
    public static double solution(String str) {
        Stack<Double> numStack = new Stack<>();
        Stack<Character> signalStack = new Stack<>();
        int index = 0;// 记录已经执行的符号数
        int len = str.length();
        while (index < len) {
            char c = str.charAt(index); // 取出这一步的符号
            if (c == '(') {
                signalStack.push(c);// 若是左括号就进栈
            }
            // 否则要先判断优先级
            else if (c == '+' || c == '-' || c == '*' || c == '/') {
                int currOperLevel = getOperlevel(c);// 当前符号的优先级
                while (true) {
                    int stackOperLevel = 0;// 栈顶元素的优先级
                    if (!signalStack.isEmpty()) {
                        Object obj = signalStack.peek();
                        stackOperLevel = getOperlevel((char) obj);
                    }
                    // 若当前元素优先级大于栈顶元素的优先级则入栈
                    if (currOperLevel > stackOperLevel) {
                        signalStack.push(c);
                        break;// 直到让比自己优先级高的符号都出栈运算了再把自己进栈
                    } else {// 不能入栈就进行计算
                        try {
                            char optemp = '0';
                            double num1 = 0;
                            double num2 = 0;
                            if (!signalStack.isEmpty()) {
                                optemp = (char) signalStack.pop();// 取出优先级大的那个符号
                            }
                            if (!numStack.isEmpty()) {
                                num1 = (double) numStack.pop();
                                num2 = (double) numStack.pop();// 取出数据栈中的两个数
                            }
                            numStack.push(caculateResult(optemp, num2, num1));// 将算出来的结果数据再次进入数据栈
                        } catch (Exception e) {
                            // TODO: handle exception
                            e.printStackTrace();
                        }
                    }
                }
            } else if (c == ')') {// 右括号就返回栈顶元素，右括号是不进栈的
                while (true) {
                    char theop = (char) signalStack.pop();
                    if (theop == '(') {
                        break;
                    } else {
                        try {
                            double num1 = (double) numStack.pop();
                            double num2 = (double) numStack.pop();
                            numStack.push(caculateResult(theop, num2, num1));// 运算括号内的内容
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }
            } else if (c >= '0' && c <= '9') {
                int tempIndex = index + 1;
                while (tempIndex < len) {
                    char temp = str.charAt(tempIndex);// 取字符串中处于当前字符的下一位
                    if ((temp >= '0' && temp <= '9') || temp == '.') {
                        tempIndex++;// 若为数字则继续向后取
                    } else {
                        break;// 证明数字去完
                    }
                }
                String numstr = str.substring(index, tempIndex);// 截取这个字符串则为两个符号之间的数字
                try {
                    double numnum = Double.parseDouble(numstr);// 将数字转换成整型便于运算
                    numStack.push(numnum);
                    index = tempIndex - 1;
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            index++;
        }
        // 检查符号栈是否为空
        while (true) {
            Object obj = null;
            if (signalStack.isEmpty() == false) {
                obj = signalStack.pop();
            }
            if (obj == null) {
                break;// 为空证明运算已结束
            } else {// 不为空就出栈运算
                char opterTemp = (char) obj;
                double num1 = (double) numStack.pop();
                double num2 = (double) numStack.pop();
                numStack.push(caculateResult(opterTemp, num2, num1));
            }
        }
        double result = 0;
        try {
            result = (double) numStack.pop();
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        return result;
    }

    //计算加减乘除余
    private static Double caculateResult(char optemp, double num1, double num2) {

        switch (optemp) {
            case '+':
                return num1 + num2;
            case '-':
                return num1 - num2;
            case '*':
                return num1 * num2;
            case '/':
                return num1 / num2;
        }
        return 0.0;
    }

    //返回符号优先级
    private static int getOperlevel(char c) {

        switch (c) {
            case '(':
                return 0;
            case '+':
            case '-':
                return 1;
            case '*':
            case '/':
                return 2;
            default:
                return 0;
        }
    }
}