import java.util.HashSet;
import java.util.Iterator;

public class HashSetDemo4 {
    public static void main(String[] args) {
        HashSet set = new HashSet();
        set.add("A");
        set.add("a");
        set.add("B");
        set.add("b");
        System.out.println(set);

        Iterator iterator = set.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }

    }
}