How to check if a string is numeric? [duplicate]

Answer 1

public static boolean isNumeric(String string) {
    if (string == null || string.isEmpty()) {
        return false;
    }
    int i = 0;
    int stringLength = string.length();
    if (string.charAt(0) == '-') {
        if (stringLength > 1) {
            i++;
        } else {
            return false;
        }
    }
    if (!Character.isDigit(string.charAt(i))
            || !Character.isDigit(string.charAt(stringLength - 1))) {
        return false;
    }
    i++;
    stringLength--;
    if (i >= stringLength) {
        return true;
    }
    for (; i < stringLength; i++) {
        if (!Character.isDigit(string.charAt(i))
                && string.charAt(i) != '.') {
            return false;
        }
    }
    return true;
}