HashSet: A set-based collection that stores unique elements. No duplicate values allowed.
Example:

import java.util.HashSet;
HashSet set = new HashSet<>();
set.add("Apple");
set.add("Banana");
set.add("Cherry");
set.add("Apple"); // Duplicate
System.out.println(set);
set.remove("Banana");
System.out.println(set);
for (String fruit : set) {
 System.out.println(fruit);
}