How to sum String values of an array, retrieved from checkbox?

Question

I have certain JSP code, wherein I can select multiple checkboxes and then I am supposed to add the values of the selected elements.

However, due to the elements being retrieved are in String format, I get a NumberFormatException when I try to do this -

String chooseRight[] = request.getParameterValues("id");

if(chooseRight != null && chooseRight.length != 0){
    int sum =0;
         out.println("The sum is: ");
    for (int i = 0; i < chooseRight.length; i++) {
        sum += Integer.parseInt(chooseRight[i]);
        out.println(sum);
    }
}

How can I possibly display int or float value in out.print(sum); ?

Answer 1

Hi you can use typeof of to validate type in javascript such as

typeof "123"; // return string
typeof 123;// return number
typeof new Object(); // return object

Hope this info helped you out

Check out more about type checking in : http://www.avlabz.com/2013/01/geekyjs-javascript-strict-type-checking-plugin/

Answer 2

I don't think it's the out.println(sum); that is the problem. sum is declared as an int and will stay that way. The error must happen in Integer.parseInt() , which in turn must be caused by chooseRight containing strings that can't be parsed as integers.

See the docs for Integer.parseInt() , which state:

Throws: NumberFormatException - if the string does not contain a parsable integer.