1. What is HashSet collection in java?
- HashSet class implements the Set interface, backed by a hash table.
- HashSet contains the unique elements.
- HashSet does not contains any duplicate keys
- HashSet can have only 1 null key.
- HashSet does not maintained the order of elements or keys.
- HashSet is UnSynchronized and not thread safe.
- Iterator of HashSet is fail-fast.
- Iterator will throw ConcurrentModificationException, if HashSet modified at any time after the iterator is created, in any way except through the iterator’s own remove method.
- HashSet offers constant time performance for the basic operations like add, remove, contains and size.
2. HashSet collection class hierarchy:
3. Program – hashset collection having String objects in java (example)
package org.learn.collection.set.hset; import java.util.HashSet; import java.util.Set; public class DemoHashSet { public static void main(String[] args) { Set<String> setSports = new HashSet<>(); setSports.add( "Tennis" ); setSports.add( "Cricket" ); setSports.add( "Tennis" ); setSports.add( null ); setSports.add( "Basketball" ); setSports.add( "Cricket" ); setSports.add( null ); setSports.add( "Basketball" ); setSports.add( "Golf" ); setSports.add( "Boxer" ); System.out.println( "HashSet collection - Unique sports list:\n" + setSports); } } |
4. Output – hashset collection having String objects in java (example)
HashSet collection - Unique sports list: [null, Tennis, Cricket, Golf, Basketball, Boxer] |