// This program is an example of pulling a number apart digit by digit
// and also contains the general form for pulling a String apart 
// character by character

public class ContainsDigit {
   public static void main(String[] args) {
      // Example pulling string apart:
      String s = "hello";
      for (int i = 0; i < s.length(); i++) {
         char c = s.charAt(i);
         // Now, we can work with the specific character, c
      }
      
      System.out.println("contains7 for 45 : " + contains7(45));
      System.out.println("contains7 for 879 : " + contains7(879));
      
   }
   
   // Returns whether a number has a 7 digit in it anywhere
   public static boolean contains7(int num) {
      // num = Math.abs(num);     --> only needed if num can be < 0

      // while (digit != 7) {     --> a natural test that actually turns out to be hard to create a solution with

      // keep going while 'num' still has digits left to look through
      while (num > 0) {  // num != 0 works too
         int digit = num % 10;  // the digit from the ones place
         // Now, we can work with the specific digit
         
         // work with that digit. For this problem, we want to know if we found a 7
         if (digit == 7) {
            // early return : we can stop looking if we find a 7 -- return true and bail out of the method
            return true;
         }
         
         num = num / 10; // the rest of the digits, shifted to the right by one place
      }
      
      // however, we have to wait until after the while loop to know that the number contains no 7s anywhere
      return false;
   }
}