我的翻译语言似乎不识别“”符号并返回错误 . 我的代码出了什么问题？

我编写了一个解释器，它将 String 作为指令集 . 该指令集声明了一组变量并返回其中一个变量 . 示例指令集将是：

A = 2
B = 8
C = A + B
C

这应该返回变量c并在控制台中打印 10 . 前提条件是左侧必须始终是一个字母，右侧只能包含一个数字或添加两个数字，并且return语句必须始终是一个变量 .

我编写了以下代码来执行此操作：

public class Interpreter2 {

public static int Scanner() {
    int returnStatement = 0;
    String num1;
    String num2;
    int sum = 0;
    ArrayList<String> variables = new ArrayList<String>();
    ArrayList<Integer> equals = new ArrayList<Integer>();
    //Input instruction set in the quotation marks below
    String input = "A = 2\n B = 8\n C = A + B\n C";
    String[] lines = input.split("\n"); //Split the instruction set by line

    for (String i : lines) {
        i = i.replaceAll("\\s", "");
        if (i.contains("=")) {          //If the line has an equals, it is a variable declaration   
            String[] sides = i.split("="); //Split the variable declarations into variables and what they equal
            variables.add(sides[0]);

            if (sides[1].contains("\\+")) { //If the equals side has an addition, check if it is a number or a variable. Convert variables to numbers and add them up
                String[] add = sides[1].split("\\+"); 
                num1 = add[0];
                num2 = add[1];
                for (int j = 0; j < variables.size(); j++) {
                    if (variables.get(j).equals(num1)) {    
                        num1 = Integer.toString(equals.get(j));
                    }   
                } 
                for (int k = 0; k < variables.size(); k++) {
                    if (variables.get(k).equals(num2)) {    
                        num2 = Integer.toString(equals.get(k));
                    }
                }
                sum = Integer.parseInt(num1) + Integer.parseInt(num2);
                equals.add(sum);
            }else { //If the equals side has no addition, it is simply equals to the variable
                equals.add(Integer.parseInt(sides[1]));
            }

        }else { //If the line does not have an equals, it is a return statement
            for (int l = 0; l < variables.size(); l++) {
                if (variables.get(l).equals(i)) {   
                    returnStatement = equals.get(l);
                }
            }
        }

    }
     return returnStatement;
}


public static void main(String[] args) {
        System.out.println(Scanner());
    }
}

然而，这给出了错误

Exception in thread "main" java.lang.NumberFormatException: For input string: "A+B"

这指向第39行：

else { 
     equals.add(Integer.parseInt(sides[1]));
     }

这让我觉得我的 if 语句判断该行中是否有"+"符号无法正常工作 . 任何人都可以看到我_32507可能是一个巨大的混乱 .