Best implementation for an isNumber(string) method

Question

In my limited experience, I\'ve been on several projects that have had some sort of string utility class with methods to determine if a given string is a number. The idea h

Answer 1

A modified version of my previous answer:

public static boolean isInteger(String in)
{
    if (in != null)
    {
        char c;
        int i = 0;
        int l = in.length();
        if (l > 0 && in.charAt(0) == '-')
        {
            i = 1;
        }
        if (l > i)
        {
            for (; i < l; i++)
            {
                c = in.charAt(i);
                if (c < '0' || c > '9')
                    return false;
            }
            return true;
        }
    }
    return false;
}