Difference between HashSet HashMap
Answer: Below are the differences:
| HashSet | HashMap |
| HashSet implements Set interface and it is backed by hash table (actually HashMap instance) | HashMap is a Hash table based implementation of Map interface |
| HashSet store objects | HashMap store object as key and value pair |
| HashSet doesn’t allow duplicate element but null values are allowed | HashMap does not allows duplicate key but null key and values are allowed |
| This interface doesn’t guarantee that order will remain constant over the time | Ordering of the element is not guaranteed over the time |
Please have java class example below:
import java.util.HashMap; import java.util.HashSet; import java.util.Map.Entry; import java.util.Set; public class HashSetMapTest { public static void main(String[] args) { HashMap<String, String> hashMap = new HashMap<String, String>(); hashMap.put("Java", "Java"); hashMap.put("Honk", "Honk"); hashMap.put("Test", "Test"); hashMap.put("Test", "Test"); hashMap.put(null,null); hashMap.put("abc",null); hashMap.put("def",null); System.out.println("HashMap example:\n"); Set<Entry<String, String>> set = hashMap.entrySet(); for (Entry<String, String> entry : set) { System.out.println("Key: "+entry.getKey() +" Value: "+entry.getValue()); } System.out.println("\nHashMap example:\n"); HashSet<String> hashSet = new HashSet<String>(); hashSet.add("Java Honk"); hashSet.add("Java Honk"); hashSet.add(null); hashSet.add(null); for (String string : hashSet) { System.out.println("Value: "+string); } } }
Output:
