How can I evaluate the expression from the string?

Question

I want to evaluate the expression from a string..

public static void main(String[] args) {

        String test = "2+3";
        System.out.println(Integer.parseInt(test));
    }

It returns me a NumberFormatException error..How do I fix this?

Answer 1

That won't work with basic java (AFAIK), maybe with some expression evaluator library. You have to parse the string. E.g.:

String[] nums = string.split("+");
List<Integer> numbers = new ArrayList<Integer>();
for(String num : nums) {
    numbers.add(Integer.parseInt(num));
int result = addNumbers(numbers);

Where addNumbers is a method you wrote to add numbers in a list. If you have more operations you have to parse the operators as well, building an expression tree then traversing it.