具有多个操作的Java计算器

它适用于任何单个操作,–,*和/.

我的问题是解决一个更大的等式,如10 – 10/5 3.
然而,它确实正确地解决了10/5 65 * 2.
原因是每个部分,数字和操作都被拆分为字符串数组.每次操作完成后,数字和操作将替换为该等式的结果.可能看起来更令人困惑,但我想不出更好的方法.它无法解决其他方程的原因是因为我将字符串映射回字符串数组.

字符串数组的示例
防爆. 10 – 10/5 3
String = {10,10,/,5,3}
在操作之后先进行除法,然后从左到右减去然后加法
String = {8,8,2,5}

这是我的代码,有人请帮助我：

修订
修改,现在它适用于上面,但仍然有一些LONG方程的麻烦.
一个简短的例子是它解决了2 * 2 * 2 * 2除以5就好了但是如果改变的话
10 – 2 * 2 * 2 * 2除以5我得到了错误的答案.

public class Matheq {

String fnum = null;
String lnum = null;
String total = null;

public String Matheq(String mathoperation) {

    String mathoperation= "6 * 3 - 4 * 2";

    mathoperation = mathoperation.replaceAll(",","");
    mathoperation = mathoperation.replaceAll("plus","+");
    mathoperation = mathoperation.replaceAll("minus","-");
    mathoperation = mathoperation.replaceAll("times","*");
    mathoperation = mathoperation.replaceAll("divided by","dividedby");
    mathoperation = mathoperation.replaceAll("percent of","percentof");
    String[] splitstr = mathoperation.split(" ");
    while(splitstr.length>1){
    for(int i=0; i<splitstr.length; i++) {
        System.out.println("Get value: " + splitstr[i]);
        if(splitstr[i].indexOf("percentof") >= 0) {
        String buildit = splitstr[i-1] + " percent of " + splitstr[i+1];
        String done = math(buildit);
        System.out.println("Percentage operation: " + splitstr[i-1] + " percent of " + splitstr[i+1] + "=" + done);
        splitstr[i] = done;
        splitstr[i-1] = "";
        splitstr[i+1] = "";
        ArrayList<String> list = new ArrayList<String>();
        for(String s : splitstr){
            if(!s.equals("")){
                list.add(s);
            }
        }
        splitstr = list.toArray(new String[list.size()]);
        }
    }
    for(int i=0; i<splitstr.length; i++) {
        System.out.println("Get value: " + splitstr[i]);
        if(splitstr[i].indexOf("dividedby") >= 0) {
            String buildit = splitstr[i-1] + " divided by " + splitstr[i+1];
            String done = math(buildit);
            System.out.println("Division operation: " + splitstr[i-1] + " divided by " + splitstr[i+1] + "=" + done);
            splitstr[i] = done;
            splitstr[i-1] = "";
            splitstr[i+1] = "";
            ArrayList<String> list = new ArrayList<String>();
            for(String s : splitstr){
                if(!s.equals("")){
                    list.add(s);
                }
            }
            splitstr = list.toArray(new String[list.size()]);
        }
    }
    for(int i=0; i<splitstr.length; i++) {
        System.out.println("Get value: " + splitstr[i]);
        if(splitstr[i].indexOf("*") >= 0) {
            String buildit = splitstr[i-1] + " * " + splitstr[i+1];
            String done = math(buildit);
            System.out.println("Multiplication operation: "+ splitstr[i-1] + " * " + splitstr[i+1] + "=" + done);
            splitstr[i] = done;
            splitstr[i-1] = "";
            splitstr[i+1] = "";
            ArrayList<String> list = new ArrayList<String>();
            for(String s : splitstr){
                if(!s.equals("")){
                    list.add(s);
                }
            }
            splitstr = list.toArray(new String[list.size()]);
        }
    }
    for(int i=0; i<splitstr.length; i++) {
            System.out.println("Get value: " + splitstr[i]);
        if(splitstr[i].indexOf("+") >= 0) {
            String buildit = splitstr[i-1] + " + " + splitstr[i+1];
            String done = math(buildit);
            System.out.println("Addition operation: " + splitstr[i-1] + " + " + splitstr[i+1] + "=" + done);
            splitstr[i] = done;
            splitstr[i-1] = "";
            splitstr[i+1] = "";
            ArrayList<String> list = new ArrayList<String>();
            for(String s : splitstr){
                if(!s.equals("")){
                    list.add(s);
                }
            }
            splitstr = list.toArray(new String[list.size()]);
        }
    }
        for(int i=0; i<splitstr.length; i++) {
            System.out.println("Get value: " + splitstr[i]);
            if(splitstr[i].indexOf("-") >= 0) {
            String buildit = splitstr[i-1] + " - " + splitstr[i+1];
            String done = math(buildit);
            System.out.println("Subtraction operation: " + splitstr[i-1] + " - " + splitstr[i+1] + "=" + done);
            splitstr[i] = done;
            splitstr[i-1] = "";
            splitstr[i+1] = "";
            ArrayList<String> list = new ArrayList<String>();
            for(String s : splitstr){
                if(!s.equals("")){
                    list.add(s);
                }
            }
            splitstr = list.toArray(new String[list.size()]);
        }   
    }
    for(int i=0; i<splitstr.length; i++) {  
        System.out.println("Final operation: " + total + " " + splitstr[i]);
    }
    }
    return total;

}

private String math(String mathoperation) {
    // TODO Auto-generated method stub
    if(mathoperation.contains("percent of")){
        mathoperation = mathoperation.replaceAll("percent of","%");
        int str = mathoperation.indexOf("%");
        System.out.println(str);
        fnum = mathoperation.substring(0,str-1);
        fnum = fnum.replaceAll(" ","");
        fnum = "." + fnum;
        System.out.println(fnum);
        double intfnum = Double.parseDouble(fnum);
        System.out.println(intfnum);
        int lastind = mathoperation.length();
        System.out.println(lastind);
        lnum = mathoperation.substring(str+1,lastind);
        lnum = lnum.replaceAll(" ","");
        System.out.println(lnum);
        double intlnum = Double.parseDouble(lnum);
        System.out.println(intlnum);
        double tot = intlnum * intfnum;
        System.out.println(tot);
        total = Double.toString(tot);
        if(total.length() == 3){
            total = total + "0";
        }
        if(total.length() > 5){
            total = total.substring(0,4);
        }
        total = total.replace("0.","");
        System.out.println("Total:" + total);
        } else 
    if(mathoperation.contains("-")){
        int str = mathoperation.indexOf("-");
        System.out.println(str);
        fnum = mathoperation.substring(0,"");
        System.out.println(fnum);
        double intfnum = Double.parseDouble(fnum);
        System.out.println(intfnum);
        int lastind = mathoperation.length();
        System.out.println(lastind);
        lnum = mathoperation.substring(str+1,"");
        System.out.println(lnum);
        double intlnum = Double.parseDouble(lnum);
        System.out.println(intlnum);
        double tot = intfnum - intlnum; 
        System.out.println(tot);
        total = Double.toString(tot);
        System.out.println(total);
        } else 
    if(mathoperation.contains("+")){
        int str = mathoperation.indexOf("+");
        System.out.println(str);
        fnum = mathoperation.substring(0,"");
        System.out.println(lnum);
        double intlnum = Double.parseDouble(lnum);
        System.out.println(intlnum);
        double tot = intfnum + intlnum; 
        System.out.println(tot);
        total = Double.toString(tot);
        System.out.println(total);
        } else 
    if(mathoperation.contains("*")){
    int str = mathoperation.indexOf("*");
    System.out.println(str);
    fnum = mathoperation.substring(0,str-1);
    fnum = fnum.replaceAll(" ","");
    System.out.println(fnum);
    double intfnum = Double.parseDouble(fnum);
    System.out.println(intfnum);
    int lastind = mathoperation.length();
    System.out.println(lastind);
    lnum = mathoperation.substring(str+1,lastind);
    lnum = lnum.replaceAll(" ","");
    System.out.println(lnum);
    double intlnum = Double.parseDouble(lnum);
    System.out.println(intlnum);
    double tot = intfnum * intlnum; 
    System.out.println(tot);
    total = Double.toString(tot);
    System.out.println(total);
    } else
    if(mathoperation.contains("divided by")){
    mathoperation = mathoperation.replaceAll("divided by","/");
    int str = mathoperation.indexOf("/");
    System.out.println(str);
    fnum = mathoperation.substring(0,"");
    System.out.println(lnum);
    double intlnum = Double.parseDouble(lnum);
    System.out.println(intlnum);
    double tot = intfnum / intlnum; 
    System.out.println(tot);
    total = Double.toString(tot);
    System.out.println(total);
    } else {
        total = null;
    }
    return total;
}

}