Answer:
The method is as follows:
public static void randomStar(Random r, int num) {
  int n;
  do {
    n = 5 + r.nextInt(15);
    for(int count = 0; count < n; count++){
      System.out.print("*");
    }
    System.out.println();
  } while(n < num);
}
Explanation:
This defines the method
public static void randomStar(Random r, int num) {
This declares n as integer
  int n;
The following is repeated until n >= num
  do {
This generates a random number for n (5 and 19)
    n = 5 + r.nextInt(15);
The following loop prints n *'s
    for(int count = 0; count < n; count++){
      System.out.print("*");
    }
This prints n
    System.out.println();
  } while(n < num); The loop is repeated as long as the condition is valid
}
