class ELUtils {

    public static boolean isNumericString(String s) {
        if (s == null) return false;
        char[] characters = s.toCharArray();
        for (int charIndex = 0; charIndex < characters.length; charIndex++) {
            char c = characters[charIndex];
            if (!Character.isDigit(c)
                    && !((charIndex == 0)
                            && ((c == '-') || (c == '+'))
                        )) {
                return false;
            }
        }
        return true;
    }

    private  ELUtils();

}