In this article, we will discuss how to find size or length of HashSet
HashSet :
We can use, size() method of Collection interface to find size of an HashSet which
- stores only unique elements
- allows maximum of one null element
- stores elements in random-order
To get size of HashSet using size() method :
FindSizeOfHashSet.java
package in.bench.resources.java.collections; import java.util.HashSet; import java.util.Iterator; public class FindSizeOfHashSet { public static void main(String[] args) { // creating HashSet object of type String HashSet<String> hs = new HashSet<String>(); // adding elements to HashSet object hs.add("Sundar Pichai"); hs.add("Satya Nadella"); hs.add("Shiv Nadar"); hs.add("Shantanu Narayen"); hs.add("Sundar Pichai"); // duplicate object hs.add("Francisco D’Souza"); hs.add(null); // one null is allowed hs.add(null); // Again, null is allowed - duplicate int hashSetSize = hs.size(); System.out.println("Size of an HashSet is : " + hashSetSize); // Iterating using Iterator of Collection interface System.out.println("\n\nIterating HashSet elements\n"); Iterator<String> itr = hs.iterator(); while(itr.hasNext()) { System.out.println(itr.next()); } } }
Output:
Size of an HashSet is : 6 Iterating HashSet elements null Shantanu Narayen Shiv Nadar Sundar Pichai Satya Nadella Francisco D’Souza
From above example, HashSet
- doesn’t allow duplicate elements
- maximum of one null object is allowed
- while iterating, retrieve elements in random-order
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/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/Iterator.html
- https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html
Happy Coding !!
Happy Learning !!