Write a method starString that takes an integer โnโ as an argument and returns a string of stars (asterisks) 2^n long (i.e., 2 to the nth power).
Task is solved in two ways: 1- for loop, 2- recursive
Performance of recursive increases for higher power of 2. StringBuilder is prefered as multiple string concatination is required. Since single thread is running, StringBuffer is not prefered.
Requirement: Java 1.8+, Maven 3.2.5+