Set in Java

import

import java.util.Set;
import java.util.HashSet;

Set

Set have its implementation in various classes like HashSet , TreeSet , LinkedHashSet .

// Hashset Random Sorting
Set<T> set = new HashSet<T>();

// TreeSet - By compareTo() or Comparator
TreeSet<T> sortedSet = new TreeSet<T>();

// LinkedHashSet - Insertion Order
LinkedHashSet<T> linkedhashset = new LinkedHashSet<T>();

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

set.add(12); 
set.add(13);

Delete all the elements of a Set

set.clear();
//Removes all objects from the collection.

set.remove(0); 
// Removes first occurrence of a specified object from the collection

Check size

set.size(); 
//Returns the number of elements in the collection

set.isEmpty();
//Returns true if the set has no elements