How to find length of long integer value using String class

import java.util.Scanner;

//Define functional interface lengthOflongInt
interface lengthOflongInt {
	public int lenOfLong(long a);
}

public class LengthOfLongInteger {

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		@SuppressWarnings("resource")
		Scanner inpLongInt = new Scanner(System.in);

		// Input a long integer
		System.out.print("Enter long Integer=");
		long longNum = inpLongInt.nextLong();
		System.out.println("The long integer is=" + longNum);

		// Define lambda expression lint which returns length
		lengthOflongInt lint = ((longInt) -> {
			String longIntToStr = String.valueOf(longInt);
			return (longIntToStr.length());
		});

		// Call the lambda expression with parameter as long integer
		System.out.println("The Length of the long integer " + longNum + " is=" + lint.lenOfLong(longNum));
		System.out.println("The Length of other long integer is=" + lint.lenOfLong(8461288490317329L));
		System.out.println("The Length of other long integer is=" + lint.lenOfLong(6536565846128717329L));
	}
}