Write a method that counts how many digits of a given number are a 7. For example, countSevens(1770) should return 2.

Complete the following file:

Numbers.java

public class Numbers { /** Counts the number of 7s in a given number @param num a number >= 0 @return the number of digits in num that are 7 */ public static int countSevens(int num) { ... } }