need help

String[] str = result.split(" ");

        int a= Integer.parseInt(str[0]);
        int b= Integer.parseInt(str[2]);
        int c=0;
        switch(str[1]){
            case "+":
                c=a+b;
                break;

            case "-":
                c=a-b;
                break;

            case "*":
                c=a*b;
                break;
        }
        str[4]=String.valueOf(c);

        for(String s:str){
        System.out.print(s);
    }