In this article, we will discuss an example of HashSet on how to delete a particular element and later deleting all elements
HashSet :
- remove(Object) –> to delete a particular element by specifying object name
- clear() –> deletes all elements present in HashSet
- Note: Both above method inherited from Collection interface
Delete an element and delete all elements :
Below HashSet example depicts,
- Deleting a particular element by specifying object name
- Deleting all elements or clearing HashSet
DeleteAndDeleteAllElementsOfHashSet.java
package in.bench.resources.java.collections; import java.util.HashSet; public class DeleteAndDeleteAllElementsOfHashSet { public static void main(String[] args) { // creating HashSet object of type String HashSet<String> hs = new HashSet<String>(); // adding elements to HashSet object - 8 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 System.out.println("Size of an HashSet is : " + hs.size()); // Iterating using enhanced for-loop System.out.println("\nIterating using enhanced for-loop\n"); for(String founder : hs) { System.out.println(founder); } // deleting particular element hs.remove("Shiv Nadar"); System.out.println("\n\nHashSet size after deleting : " + hs.size()); // Iterating using enhanced for-loop System.out.println("\nAfter deleting particular object\n"); for(String founder : hs) { System.out.println(founder); } // deleting all elements hs.clear(); System.out.println("\n\nHashSet size after clearing : " + hs.size()); // Iterating using enhanced for-loop System.out.println("\nIterating after clearing \n" + hs); } }
Output:
Size of an HashSet is : 6 Iterating HashSet using enhanced for-loop null Shantanu Narayen Francisco D’Souza Shiv Nadar Satya Nadella Sundar Pichai HashSet size after deleting : 5 Iterating after deleting particular object null Shantanu Narayen Francisco D’Souza Satya Nadella Sundar Pichai HashSet size after clearing : 0 Iterating after clearing []
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 !!