import java.util.*;
public class MyClass {
public static void main(String args[]) {
Set<String> letters = new HashSet<>(Arrays.asList("a", "b", "c", "d", "a", "a"));
letters.add("x");
letters.add("y");
letters.add("a");
System.out.println(letters);
}
}
/*
run:
[a, b, c, d, x, y]
*/