Question

Can someone help me with my homework?

Answer 1

Answer:

class Main {

 public static void main(String[] args) {

   if (args.length > 0) {

     long count = args[0].chars().filter(ch -> ch == '7').count();

     System.out.println("Number of sevens " + count);

   }

 }

}

Explanation:

That would do the trick. Drop a comment if you need more explanation. It requires Java 8 because of the lambda expression. What happens is that the input is treated as a string rather than a number, because we're looking for 7's. Convert it to an array of chars, filter out only the chars that are a '7' and count them.