How to find sum of digits in an alpha numeric value

import java.util.Scanner;

public class SumOfDigitsInString {

	public static void main(String[] args) {

		Scanner inpStr = new Scanner(System.in);
		System.out.println("Enter an alphanumeric value");
		String inpLine = inpStr.nextLine();

		/*
		 * Basic validations - Checking if the string is empty, if it contains more than
		 * one string, and if it's purely numeric & has any symbols
		 */
		if (inpLine.isEmpty())
			System.out.println("Given string is empty");
		else if (inpLine.split("\\s").length > 1)
			System.out.println("Input can only contain one string");
		else if (!isValidInput(inpLine))
			System.out.println("The input should be alphanumeric or alphabetic");
		else {
			int digitSum = 0;
			digitSum = sumOfDigits(inpLine);
			inpStr.close();
			System.out.printf("The sum of all the digits in the string is %d", digitSum).println();
		}
	}

	private static boolean isValidInput(String s) {
		/*
		 * This method uses regular expressions to check if the input string is valid by
		 * checking if it only contains digits and if it has any symbols. If it doesn't
		 * purely consist of digits AND doesn't contain symbols, this method returns
		 * true i.e. the input is valid.
		 */
		boolean onlyDigitChecker = s.matches("[0-9]*$") && s.matches("[^a-zA-Z]*$");
		boolean noSymbolChecker = s.matches("^[a-zA-Z0-9]*$");
		if (!onlyDigitChecker && noSymbolChecker)
			return true;
		else
			return false;
	}

	private static int sumOfDigits(String s) {
		/*
		 * This method runs through the input string and whenever it encounters a digit,
		 * it adds it to a variable. This variable, which is the sum of digits in the
		 * strings, is returned at the end
		 */
		int digitAdder = 0;
		try {
			for (int i = 0; i < s.length(); i++) {
				char readChar = s.charAt(i);
				if ((int) readChar >= 48 && (int) readChar <= 57)
					digitAdder += ((int) readChar - 48);
			}
		} catch (Exception e) {
			System.out.printf("Exception is %s", e).println();
		}
		return digitAdder;
	}
}