web calculator based on Servlet+jsp

This time, in order to let us review the page Jump in the web, the boss gave us an unworthy task

A big copy of the world's code depends on how you copy it

First of all, the algorithm I think about is not a stack, but a simple one (actually, it's very complex, but I just need to know that someone else has done it well... The legendary CV method is good? Emmm, when you know there's such an algorithm but you can't write it by yourself but you can use it by yourself, it's equivalent to... You can...)

Needless to say, it's a collected regular tool class, which supports bracket operation

package pers.cal.util;

import java.util.regex.Matcher;
import java.util.regex.Pattern;
 * The bracketed version of calculator implemented by regular expression
 * @author Administrator
public class UtilArithmetic {
     * Evaluate expressions that may contain parentheses
     * @param s
     * @return
    public static String calcu(String s) {

        s = s.replaceAll(" +", "");// Eliminate the space. The space can be one or more. Replace it when you find it
        // \(left bracket \ \) right bracket means there is no other bracket within the bracket, and then it is a subgroup e surrounded by brackets
        Pattern pa = Pattern.compile("\\(([^\\(\\)]*)\\)");
        while (true) {
            Matcher ma = pa.matcher(s);
            if (ma.find() == false)
            // Calculate the parentheses first, then eliminate them
            s = s.replace(ma.group(), calcuNoParen(ma.group(1)));

        return calcuNoParen(s);

     * Calculate operations without parentheses
     * @param s2
     * @return
    public static String calcuNoParen(String s2) {
        if (s2.length() < 1)
            return s2;
        // Eliminate multiplication first
        Pattern pat = Pattern.compile("([0-9]+)\\*([0-9]+)");//0-9 one or more, multiply
        while (true) {
            Matcher mc = pat.matcher(s2);
            if (mc.find() == false)
            int res = Integer.parseInt(mc.group(1)) * Integer.parseInt(mc.group(2));
            // Calculate the result, and remove the brackets. Note that replaceAll cannot be used here
            s2 = s2.replace(mc.group(), res + "");
        // Then eliminate all addition and subtraction from left to right
        pat = Pattern.compile("([0-9]+)([\\+\\-])([0-9]+)");// 0-9 one or more, add or subtract
        while (true) {
            Matcher mc = pat.matcher(s2);
            if (mc.find() == false)
            int res = 0;
            switch (mc.group(2)) {
            case "+":
                res = Integer.parseInt(mc.group(1)) + Integer.parseInt(mc.group(3));

            case "-":
                res = Integer.parseInt(mc.group(1)) - Integer.parseInt(mc.group(3));
            // Calculate the result, and remove the brackets. Note that replaceAl cannot be used here
            s2 = s2.replace(mc.group(), res + "");
        return s2;


When calling, just use calcu()

Then the corresponding foreground jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
    <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Be based on Servlet+jsp Of Web Calculator project</title>

<link href="./css/index.css" rel="stylesheet" type="text/css" />

<script type="text/javascript">
    var cleartext = false;//Set identity value
    function getNum(num) {
        var result = document.getElementById("result");
        if (cleartext) {
            result.value = "";
            //cleartext = false;
        result.value += num;

    function getResult() {
        var result = document.getElementById("result");
        //next is the str we need
        result.value = result.value;
        //this result.value is the str we need
        //cleartext = true; / / change the ID after calculating the result
    <div class="calculator">
        <span class="copyRight">Kim Sheng Chung ®</span>

        <form action="calculator.do" method="post" name="From"
            onclick="return getResult">

            <div class="calculator-display">
                <input type="text" name="result" id="result" size="33"
                    readonly=readonly value="${ count}" >

            <div class="calculator-keys">
                <button type="button" class="all-clear" value="all-clear"

                <button type="button" value="9" onclick="getNum('(')">(</button>
                <button type="button" value="9" onclick="getNum(')')">)</button>
                <button type="button" class="operator" value="+"

                <button type="button" value="7" onclick="getNum(7)">7</button>
                <button type="button" value="8" onclick="getNum(8)">8</button>
                <button type="button" value="9" onclick="getNum(9)">9</button>

                <button type="button" class="operator" value="-"
                <button type="button" value="4" onclick="getNum(4)">4</button>
                <button type="button" value="5" onclick="getNum(5)">5</button>
                <button type="button" value="6" onclick="getNum(6)">6</button>
                <button type="button" class="operator" value="*"

                <button type="button" value="1" onclick="getNum(1)">1</button>
                <button type="button" value="2" onclick="getNum(2)">2</button>
                <button type="button" value="3" onclick="getNum(3)">3</button>

                <button type="button" class="operator" value="/"
                <button type="button" value="0" onclick="getNum(0)">0</button>
                <button type="button" class="decimal" value="."
                <button class="equal-sign" value="=" onclick="getResult('.')">=</button>



His css

html {
    font-size: 62.5%;
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    box-sizing: inherit

body {
  width: 100vw;
  min-height: 100vh;
  background-color: #B0C4DE;
  display: flex;
  justify-content: center;
  align-items: center;

.calculator {
  background: #1d1e22;
  padding:2.8rem .64rem .64rem;
  color: white;
  border-radius: .5rem;
  box-shadow: 0 .3rem 3rem .1rem rgba(0,0,0,0.6);
  position: relative;
  min-width: 40rem;

.calculator-display {
  font-size: 5rem;
  height: 80px;
  padding: 0 20px;
  background-color: #1d1e22;
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: flex-end;
button {
  height: 60px;
  border-radius: 3px;
  border: 1px solid #c4c4c4;
  font-size: 2rem;  
  background-color: #fff;


.calculator-keys {
  display: grid;
  grid-gap: 2rem;
  padding: 2rem 1.36rem;
  background-color: #fff;

.equal-sign {
  grid-row: 5 / span 1;
  grid-column: 3 / 5;
  height: 100%;
    text-align: center;
    font-size: 33px;

Look like this

El expression used

Related jar packages

xml configuration

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    id="WebApp_ID" version="2.5">



Corresponding Servlet

package pers.cal.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import pers.cal.util.UtilArithmetic;

public class CalculationServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String result = req.getParameter("result");
    //  req.setAttribute("result", "admin");
        String finalRes = result;
        result = finalRes+UtilArithmetic.calcu(result);
        HttpSession session = req.getSession();
        req.getRequestDispatcher("index.jsp").forward(req, resp);


Finally, the structure

Good night.

Have a good dream


Tags: Java calculator xml JSP

Posted on Tue, 03 Dec 2019 03:30:49 -0500 by knelson