In this article, we will discuss Set interface in detail

1. Key points about Set:

• Set doesn’t allow duplicate items
• also doesn’t maintain insertion-order

2. Set interface:

• Set is a sub-interface of Collection interface (i.e.; Set extends Collection)
• To represent a group of element/objects as a single unit/entity, where duplicates aren’t allowed
• Set allows only unique element/objects to be inserted
• Set doesn’t maintain insertion-order
• While iterating through Set, we will get items in random-order (as against insertion-order in List)
• There are 2 direct concrete classes for Set interface viz.; HashSet, LinkedHashSet and another one TreeSet (through SortedSet –> NavigableSet)
• Set interface doesn’t contain any methods but only inherited methods from Collection interface
• Present in java.util package and extends java.util.Collection interface

Source: Team BenchResources.Net

3. Below listed classes implements Set interface

• HashSet
• LinkedHashSet
• TreeSet (through SoretdSet –> NavigableSet)

4. Factors to consider while discussing any collection class

We should consider below factors while discussing any implementation class of collection framework or for that matter Map interface,

• Underlying data structure
• Duplicates are allowed or Not
• Insertion order is maintained or Not
• Whether NULL insertion is possible or Not
• If possible, how many NULL values can be inserted
• Whether collection class provide sorting, by default
• Is there any way to apply customized sorting
• Performance, while dealing with retrieval or manipulation (addition/deletion)
• By default, all methods are synchronized or Not

Related Articles:

• Set interface
• HashSet class
• LinkedHashSet class
• SortedSet interface
• NavigableSet interface
• TreeSet class
• HashSet v/s LinkedHashSet
• HashSet v/s LinkedHashSet v/s TreeSet
• List v/s Set
• HashMap v/s HashSet

References:

• https://docs.oracle.com/javase/tutorial/collections/intro/
• https://docs.oracle.com/javase/tutorial/collections/interfaces/collection.html
• https://docs.oracle.com/javase/7/docs/api/java/util/Collection.html
• https://docs.oracle.com/javase/tutorial/collections/interfaces/list.html
• https://docs.oracle.com/javase/tutorial/collections/interfaces/set.html
• https://docs.oracle.com/javase/7/docs/api/java/util/Set.html

Happy Coding !!
Happy Learning !!