What is the Set interface? The Set interface in Java is your go-to when you need a collection that stores unique elements only. No duplicates, no index-based access. -Set extends the Collection interface and lives in java.util. Its defining contract: it will never contain duplicate elements. -Internally, "duplicate" is determined by equals() and hashCode() — so you must override both when using custom objects. 1.HashSet: Use HashSet when you only care about uniqueness and O(1) average-case performance, and don't need a predictable iteration order. O(1) avg -Backed by a HashMap. Fastest for add/remove/contains. No ordering guarantee whatsoever. Example: Set < String > fruits = new HashSet <>(); fruits . add ( "Apple" ); fruits . add ( "Mango" ); fruits .…