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Java 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();
}
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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
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