Java解析字符串中的加减乘除四则运算的实现

这里分享一个工具类、这个工具类是在我写DD记账的时候用到的、那就是计算一个可运算的字符串、可直接使用java解析字符串中的四则运算、现在把这个工具类的源代码分享给大家、相信会对一些做计算器获者一些简单的运算的朋友有用、话不多说、下面直接上代码

ReportUtil.java

package com.dwtedx.income.utility;

import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Created by dwtedx(qinyl)(http://dwtedx.com) on 16/9/2.
 * Company DD博客
 * Description java字符串加法运算
 */
public class ReportUtil {

    /**
     * 格式化数字
     * @param obj 数字对象
     * @param format 格式化字符串
     * @return
     */
    public static String formatNumber(Object obj, String format) {
        if (obj == null)
            return "";

        String s = String.valueOf(obj);
        if (format == null || "".equals(format.trim())) {
            format = "#.00";
        }
        try {
            if (obj instanceof Double || obj instanceof Float) {
                if (format.contains("%")) {
                    NumberFormat numberFormat = NumberFormat.getPercentInstance();
                    s = numberFormat.format(obj);
                } else {
                    DecimalFormat decimalFormat = new DecimalFormat(format);
                    s = decimalFormat.format(obj);
                }
            } else {
                NumberFormat numberFormat = NumberFormat.getInstance();
                s = numberFormat.format(obj);
            }
        } catch (Exception e) {
        }
        return s;
    }

    /**
     * 计算字符串四则运算表达式
     * @param string
     * @return
     */
    public static String computeString(String string) {
        String regexCheck = "[\(\)\d\ \-\*/\.]*";// 是否是合法的表达式

        if (!Pattern.matches(regexCheck, string))
            return string;

        Matcher matcher = null;
        String temp = "";
        int index = -1;
        String regex = "\([\d\.\ \-\*/] \)";// 提取括号表达式
        string = string.replaceAll("\s", "");// 去除空格
        try {
            Pattern pattern = Pattern.compile(regex);
            // 循环计算所有括号里的表达式
            while (pattern.matcher(string).find()) {
                matcher = pattern.matcher(string);
                while (matcher.find()) {
                    temp = matcher.group();
                    index = string.indexOf(temp);
                    string = string.substring(0, index)
                              computeStirngNoBracket(temp)
                              string.substring(index   temp.length());
                }
            }
            // 最后计算总的表达式结果
            string = computeStirngNoBracket(string);
        } catch (NumberFormatException e) {
            return e.getMessage();
        }
        return string;
    }

    /**
     * 计算不包含括号的表达式
     * @param string
     * @return
     */
    private static String computeStirngNoBracket(String string) {
        string = string.replaceAll("(^\()|(\)$)", "");
        String regexMultiAndDivision = "[\d\.] (\*|\/)[\d\.] ";
        String regexAdditionAndSubtraction = "(^\-)?[\d\.] (\ |\-)[\d\.] ";

        String temp = "";
        int index = -1;

        // 解析乘除法
        Pattern pattern = Pattern.compile(regexMultiAndDivision);
        Matcher matcher = null;
        while (pattern.matcher(string).find()) {
            matcher = pattern.matcher(string);
            if (matcher.find()) {
                temp = matcher.group();
                index = string.indexOf(temp);
                string = string.substring(0, index)   doMultiAndDivision(temp)
                          string.substring(index   temp.length());
            }
        }

        // 解析加减法
        pattern = Pattern.compile(regexAdditionAndSubtraction);
        while (pattern.matcher(string).find()) {
            matcher = pattern.matcher(string);
            if (matcher.find()) {
                temp = matcher.group();
                index = string.indexOf(temp);
                if (temp.startsWith("-")) {
                    string = string.substring(0, index)
                              doNegativeOperation(temp)
                              string.substring(index   temp.length());
                } else {
                    string = string.substring(0, index)
                              doAdditionAndSubtraction(temp)
                              string.substring(index   temp.length());
                }
            }
        }

        return string;
    }

    /**
     * 执行乘除法
     * @param string
     * @return
     */
    private static String doMultiAndDivision(String string) {
        String value = "";
        double d1 = 0;
        double d2 = 0;
        String[] temp = null;
        if (string.contains("*")) {
            temp = string.split("\*");
        } else {
            temp = string.split("/");
        }

        if (temp.length < 2)
            return string;

        d1 = Double.valueOf(temp[0]);
        d2 = Double.valueOf(temp[1]);
        if (string.contains("*")) {
            value = String.valueOf(d1 * d2);
        } else {
            value = String.valueOf(d1 / d2);
        }

        return value;
    }

    /**
     * 执行加减法
     * @param string
     * @return
     */
    private static String doAdditionAndSubtraction(String string) {
        double d1 = 0;
        double d2 = 0;
        String[] temp = null;
        String value = "";
        if (string.contains(" ")) {
            temp = string.split("\ ");
        } else {
            temp = string.split("\-");
        }

        if (temp.length < 2)
            return string;

        d1 = Double.valueOf(temp[0]);
        d2 = Double.valueOf(temp[1]);
        if (string.contains(" ")) {
            value = String.valueOf(d1   d2);
        } else {
            value = String.valueOf(d1 - d2);
        }

        return value;
    }

    /**
     * 执行负数运算
     * @param string
     * @return
     */
    private static String doNegativeOperation(String string) {
        String temp = string.substring(1);
        if (temp.contains(" ")) {
            temp = temp.replace(" ", "-");
        } else {
            temp = temp.replace("-", " ");
        }
        temp = doAdditionAndSubtraction(temp);
        if (temp.startsWith("-")) {
            temp = temp.substring(1);
        } else {
            temp = "-"   temp;
        }
        return temp;
    }

}

调用方法

public static void main(String[] args) {
    String s = "1-7 8*2";
    s = computeString(s);
    System.out.println((int)Double.parseDouble(s));
}

以上就是整个类的代码以及使用方法、大家可以自己的运用到项目中、非常的方便