In this article, we will discuss difference between HashSet and LinkedHashSet classes in detail i.e.; HashSet v/s LinkedHashSet
1. HashSet v/s LinkedHashSet:
| HashSet | LinkedHashSet |
| Uses hashtable to store element/objects
(actually HashMap instance) | Uses combination of hashtable + LinkedList to store element/objects |
| Doesn’t maintain insertion order
i.e.; while iterating through HashSet, we will get items in random-order | Since, it uses doubly-linked list to store elements, maintains insertion-order |
| This is introduced in the original collection framework in Java 1.2 version | This is introduced in Java 1.4 version |
Q) When to use HashSet ?
- HashSet stores unique elements using hashing technique
- So, search operation is faster
- So, if business requirement is to store unique elements for faster search operation or more number of search operation without concerning insertion-order
- Then, HashSet is the very apt choice
Q) When to use LinkedHashSet ?
- This is exactly same as that of HashSet, but underlying data structure to hold items is different
- It uses doubly-linked list which allows to hold items as per insertion-order
- So, if business requirement is to store unique elements for faster search operation or more number of search operation concerning/maintaining insertion-order
- Then, LinkedHashSet is the very apt choice which maintains insertion-order
- So while iterating through LinkedHashSet, we will get items as per insertion order (as against random in HashSet)
2. Set Program using HashSet and LinkedHashSet :
SetExample.java
package in.bench.resources.collection;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.Set;
public class SetExample {
public static void main(String[] args) {
// 1. Creating HashSet object
Set<String> hashSet = new HashSet<String>();
// add few elements
hashSet.add("Vijay");
hashSet.add("Ajith");
hashSet.add("Vikram");
hashSet.add("Suriya");
System.out.println("Displaying HashSet elements"
+ " in Random-order : \n");
for(String actor : hashSet) {
System.out.println(actor);
}
// 2. Creating HashSet object
Set<String> linkedHashSet = new LinkedHashSet<String>();
// add few elements
linkedHashSet.add("Sharukh");
linkedHashSet.add("Akshay");
linkedHashSet.add("Saif");
linkedHashSet.add("Salman");
System.out.println("\nDisplaying LinkedHashSet elements"
+ " as per Insertion-order : \n");
for(String actor : linkedHashSet) {
System.out.println(actor);
}
}
}
Output:
Displaying HashSet elements in Random-order :
Ajith
Vijay
Suriya
Vikram
Displaying LinkedHashSet elements as per Insertion-order :
Sharukh
Akshay
Saif
Salman
Related Articles:
- Set interface
- HashSet class
- LinkedHashSet class
- SortedSet interface
- NavigableSet interface
- TreeSet class
- HashSet v/s LinkedHashSet
- HashSet v/s LinkedHashSet v/s TreeSet
- List v/s Set
- HashMap v/s HashSet
References:
- https://docs.oracle.com/javase/tutorial/collections/intro/
- https://docs.oracle.com/javase/tutorial/collections/interfaces/collection.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Collection.html
- https://docs.oracle.com/javase/tutorial/collections/interfaces/list.html
- https://docs.oracle.com/javase/tutorial/collections/interfaces/set.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Set.html
- https://docs.oracle.com/javase/7/docs/api/java/util/class-use/HashSet.html
- https://docs.oracle.com/javase/7/docs/api/java/util/HashSet.html
- https://docs.oracle.com/javase/7/docs/api/java/util/LinkedHashSet.html
- http://docs.oracle.com/javase/7/docs/api/index.html?java/util/class-use/LinkedHashSet.html
Happy Coding !!
Happy Learning !!
