Java写的有运算顺序的计算器(不含括号)

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Calculator
{
    public static void main(String args[])throws Exception
    {
        int yunSuanFu;
        float result;
        String str = new BufferedReader(new InputStreamReader(System.in)).readLine();
        char[] ch = str.toCharArray();
        yunSuanFu = Tool.yunSuanFu(ch);
        char[] fuHao = Tool.getFuHao(ch,yunSuanFu);
        String[] sub = Tool.getSub(ch,str,yunSuanFu);
        float[] zhi = Tool.getZhi(sub,yunSuanFu);
        result = Tool.work(zhi,fuHao,yunSuanFu);
        System.out.println(result);
    }    
}

class Tool
{
    public static int yunSuanFu(char[] ch)
    {
        int i;
        int yunSuanFu = 0;
        for(i = 0; i < ch.length; i++){
            if((ch[i] == '+') || (ch[i] == '-') || (ch[i] == '*') || (ch[i] == '/'))
            {
                yunSuanFu++;
            }
        }
        return yunSuanFu;
    }

    public static char[] getFuHao(char[] ch, int yunSuanFu){
        int i;
        int j = 0;
        char[] fuHao = new char[yunSuanFu];
        for(i = 0; i < ch.length; i++){
            if((ch[i] == '+') || (ch[i] == '-') || (ch[i] == '*') || (ch[i] == '/'))
            {        
                fuHao[j] = ch[i];
                j++;
            }
        }
        return fuHao;
    }

    public static String[] getSub(char[] ch, String str, int yunSuanFu)
    {
        int i;
        int j = 0;
        int begin = 0;
        String[] sub = new String[yunSuanFu+1];
        for(i = 0; i < ch.length; i++){
            if((ch[i] == '+') || (ch[i] == '-') || (ch[i] == '*') || (ch[i] == '/'))
            {
                sub[j] = str.substring(begin, i);        
                begin = i + 1;
                j++;
            }
        }
        sub[j] = str.substring(begin,ch.length);
        return sub;
    }

    public static float[] getZhi(String[] sub, int yunSuanFu)
    {
        int i;
        float[] zhi = new float[yunSuanFu+1];
        for(i = 0; i <= yunSuanFu; i++)
        {
            zhi[i] = Float.parseFloat(sub[i]);
        }
        return zhi;
    }

    public static float work(float[] zhi, char[] fuHao, int yunSuanFu)
    {
        int k;
        int tag = 0;
        int index = 0;
        float a;
        float b;
        for(k = 0; k < yunSuanFu; k++)
        {
            if((fuHao[k] == '+') || (fuHao[k] == '-'))
            {
                fuHao[index] = fuHao[k];
                zhi[index+1] = zhi[k+1];
                index++;
            }
            else if(fuHao[k] == '*')
            {
                if(tag + 1 == k)
                {
                    zhi[index] = zhi[index] * zhi[k+1];
                }
                else
                {
                    zhi[index] = zhi[k] * zhi[k+1];
                }
                tag = k;
            }
            else
            {
                if(tag + 1 == k)
                {
                    zhi[index] = zhi[index] / zhi[k+1];
                }
                else
                {
                    zhi[index] = zhi[k] / zhi[k+1];
                }
                tag = k;
            }
        }

        if((fuHao[yunSuanFu-1] == '+') || (fuHao[yunSuanFu-1] == '-'))
        {
            zhi[index] = zhi[yunSuanFu];
        }

        a = zhi[0];
        for(k = 0; k < index; k++)
        {
            b = zhi[k+1];
            if(fuHao[k] == '+')
            {
                a += b;
            }
            else
            {
                a -= b;
            }
        }
        return a;
    }    
}