Java Language Sets Basics of Set
Example
What is a Set?
A set is a data structure which contains a set of elements with an important property that no two elements in the set are equal.
Types of Set:
- HashSet: A set backed by a hash table (actually a HashMap instance)
- Linked HashSet: A Set backed by Hash table and linked list, with predictable iteration order
- TreeSet: A NavigableSet implementation based on a TreeMap.
Creating a set
Set<Integer> set = new HashSet<Integer>(); // Creates an empty Set of Integers
Set<Integer> linkedHashSet = new LinkedHashSet<Integer>(); //Creates a empty Set of Integers, with predictable iteration order
Adding elements to a Set
Elements can be added to a set using the add() method
set.add(12); // - Adds element 12 to the set
set.add(13); // - Adds element 13 to the set
Our set after executing this method:
set = [12,13]
Delete all the elements of a Set
set.clear(); //Removes all objects from the collection.
After this set will be:
set = []
Check whether an element is part of the Set
Existence of an element in the set can be checked using the contains() method
set.contains(0); //Returns true if a specified object is an element within the set.
Output: False
Check whether a Set is empty
isEmpty() method can be used to check whether a Set is empty.
set.isEmpty(); //Returns true if the set has no elements
Output: True
Remove an element from the Set
set.remove(0); // Removes first occurrence of a specified object from the collection
Check the Size of the Set
set.size(); //Returns the number of elements in the collection
Output: 0
