Java HashSet class

• uses hashtable to store the elements.It extends AbstractSet class and implements Set interface.
• contains unique elements only.

Difference between List and Set:

List can contain duplicate elements whereas Set contains unique elements only.

Hierarchy of HashSet class:

Example of HashSet class:

1. import java.util.*;  
2. class TestCollection9{  
3.  public static void main(String args[]){  
4.    
5.   HashSet<String> al=new HashSet<String>();  
6.   al.add("Ravi");  
7.   al.add("Vijay");  
8.   al.add("Ravi");  
9.   al.add("Ajay");  
10.   
11.   Iterator<String> itr=al.iterator();  
12.   while(itr.hasNext()){  
13.    System.out.println(itr.next());  
14.   }  
15.  }  
16. }  

Output:Ajay
       Vijay
       Ravi