What is a HashSet in Java and how does it differ from HashMap?
HashMap is an associative map collection. You store values by putting them in the map with a key object. The key object is associated with the value object. If you put another object in the map using the same key object, the new value object replaces the previous one associated with the key. On the other hand, you can store the same or equivalent value objects multiple times, by associating with different keys. HashSet is a collection backed by a HashMap and stores a set of objects. There is no associate mapping for the user to use. You just add or remove from the set. A set collection is similar to a mathematical set, in that no duplicates are allowed. Thus adding the same or equivalent objects to the same HashSet will not result in multiple references being stored. The “extra” calls to add() will simple return without doing anything. You simply call add(object), remove(object), and iterator() to get an Iterator instance. Note that the performance of the HashSet is based on the perfor
