HashSet

 

 

• The HashSet class implements the Set interface.
• It makes no guarantee that the order of elements will remain constant over time.
• This class is not synchronized and permits a null element.
• This class offers constant time performance for the basic operations (add, remove, contains and size), assuming the hash function disperses the elements properly among the buckets.
• To prevent unsynchronized access to the Set: Set s = Collections.synchronizedSet(new HashSet(...));

Below is a HashSet Example showing how collections are manipulated using a HashSet

 import java.util.*;

 public class HashSetExample{
	 
	 private static String names[] = { "bob", "hemanth", "hhh", "hero", "shawn", "bob",
	 "mike", "Rick", "rock", "hemanth", "mike", "undertaker" };

	 public static void main( String args[] ){
		 ArrayList aList;

		 aList = new ArrayList( Arrays.asList( names ) );
		 System.out.println( "The names elements " + aList );
		 
		 HashSet ref = new HashSet(aList); // create a HashSet
		 Iterator i = ref.iterator();
		 System.out.println();
		 System.out.print("Unique names are: " );
		 while ( i.hasNext() )
			 System.out.print( i.next() + " " );

		 System.out.println();

	 }
 }

     

Output

The names elements [bob, hemanth, hhh, hero, shawn, bob, mike, Rick, rock, hemanth, mike, undertaker]

Unique names are: hhh hero bob Rick shawn hemanth rock mike undertaker

 

Download HashSetExample.java