Java 使用正则表达式拆分字符串来计算字符串中的数学表达式

我需要一些字符串中的数学表达式

到目前为止，我的代码只适用于正数

我使用正则表达式将字符串拆分为两个单独的数组。我能把所有的数学符号分成一个数组，把所有的数字分成另一个数组。但我不确定如何处理负数。（我不懂正则表达式，我只是放了一些东西，它起作用了，但不适用于负数）

无论如何，这是我的代码，提前谢谢`

    boolean mybool = true;
    String str = "1.0+2.0+3.0+4.0";
    String[] numarray = str.split("[-+/%*]");
    String[] signarray = str.split("[0123456789.]");
    double result = 0.0;
    double num1 = 0.0;
    double num2 = 0.0;

    String mystr = "";

    //Adds each element in sign array to mystr
    for(String e : signarray){
        if(e != ""){
            mystr+=e;
        }
    }

    //Assign signarray new size of length mystr
    signarray = new String[mystr.length()];


    //Cycle through each element in str and add it to signarray
    for(int i = 0; i < mystr.length(); i++){
        signarray[i] = mystr.charAt(i)+"";
    }

    //Print each element in num array
    System.out.print("Print each element in number array: ");
    for(String e : numarray){
        System.out.print(e+ " ");
    }
    System.out.println();

    System.out.print("Print each element in sign array: ");
    //print each element in sign array
    for(String e : signarray){
        System.out.print(e+ " ");
    }
    System.out.println();

    //Prints each element in sign array and element value
    for(int i = 0; i < signarray.length; i++){
        System.out.println("SignArray[" + i + "] = " + signarray[i]);
    }


    for(int i = 2; i <= numarray.length; i++){

        //this will get the first two indexes of number array
        //and store them in num1 and num1 then i use another if
        //statement to go sign array to get a sign to evaluate the
        //two nums and store the value in result.
        //hopefully you understand my logic
        if(mybool == true){


            num1 = Double.parseDouble(numarray[0]);
            num2 = Double.parseDouble(numarray[1]);
            System.out.println("num1 = " + num1);
            System.out.println("num2 = " + num2);


            if(signarray[0].equals("+")){
                result = num1 + num2;
                System.out.println("Result = num1 + num2 = " + num1 + "+" + num2 + "= " + result );
            } else if(signarray[0].equals("-")){
                result = num1 - num2;
                System.out.println("Result = num1 - num2 = " + num1 + "-" + num2 + "= " + result );
            } else if(signarray[0].equals("/")){
                result = num1 / num2;
                System.out.println("Result = num1 / num2 = " + num1 + "/" + num2 + "= " + result );
            } else if(signarray[0].equals("*")){
                result = num1 * num2;
                System.out.println("Result = num1 * num2 = " + num1 + "*" + num2 + "= " + result );
            } else if(signarray[0].equals("%")){
                result = num1 % num2;
                System.out.println("Result = num1 % num2 = " + num1 + "%" + num2 + "= " + result );
            }

            mybool = false;

        } else {

            num2 = Double.parseDouble(numarray[i-1]);
            System.out.println("Num2 = " + num2);


            if(signarray[i-2].equals("+")){
                result = result + num2;
                System.out.println("Result after math is : " + result);

            } else if(signarray[i-2].equals("-")){
                result = result - num2;
                System.out.println("Result after math is : " + result);
            } else if(signarray[i-2].equals("/")){
                result = result / num2;
                System.out.println("Result after math is : " + result);
            } else if(signarray[i-2].equals("*")){
                result = result * num2;
                System.out.println("Result after math is : " + result);
            } else if(signarray[i-2].equals("%")){
                result = result % num2;
                System.out.println("Result after math is : " + result);
            }

        }



    }`

最终我希望能够计算出这样的字符串 //String str=“3.01+2.2/4.01*7.1%4.0--2.0”

但是我不知道如何从sting中获取负数并存储在num数组中

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谢谢你的帮助

理想情况下，应该使用解析器而不是正则表达式。然而，考虑到您当前的需求，使用正面和负面的lookbehind会很简单

（1） 。运算符的前面总是有一个十进制数。因此，我们通过匹配十进制数（正查找）后出现的任何运算符来拆分参数

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String[]arguments=str.split（（？--thould-throw-（-2）最好是我会调查你的正则表达式的正面和负面外观。或者更好的是，不要使用正则表达式使用解析器。如果你在符号上分割，你永远不会得到符号。此外，
--2.0
是
-1*-2.0
你不应该使用正则表达式。你需要一个合适的扫描器，然后是一个表达式解析器将其全部删除并查找Disjkstra调车场算法或递归下降表达式解析。
Print each element in number array: 1.0 2.0 3.0 4.0 
Print each element in sign array: + + + 
SignArray[0] = +
SignArray[1] = +
SignArray[2] = +
num1 = 1.0
num2 = 2.0
Result = num1 + num2 = 1.0+2.0= 3.0
Num2 = 3.0
Result after math is : 6.0
Num2 = 4.0
Result after math is : 10.0

String[] arguments = str.split("(?<=\\d)[-+/%*]");

String[] operators = str.split("(?<!\\d)-?[0-9.]+");