Java Hashset

INTRODUCTION TO JAVA HASHSET

• The Java 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

JAVA HASHSET EXAMPLE

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