Difference between HashMap and LinkedHashMap in java?

Question

Vulpes · Answer

Sure here's one: // HashMapDemo.java import java.util.*; class HashMapDemo { public static void main(String[] args) { // create HashMap HashMap hm = new HashMap (); // put elements hm.put(Barack Obama USA); hm.put(David Cameron UK); hm.put(Pranab Mukherjee India); // print them out for (Map.Entry entry : hm.entrySet()) { System.out.println(entry.getKey() +  :  + entry.getValue()); } System.out.println(); // create LinkedHashMap LinkedHashMap lhm = new LinkedHashMap (); // put elements lhm.put(Barack Obama USA); lhm.put(David Cameron UK); lhm.put(Pranab Mukherjee India); // print them out for (Map.Entry entry : lhm.entrySet()) { System.out.println(entry.getKey() +  :  + entry.getValue()); } } } The output is: David Cameron : UK Barack Obama : USA Pranab Mukherjee : India Barack Obama : USA David Cameron : UK Pranab Mukherjee : India Notice that in the case of LinkedHashMap the entries are iterated in the order they were added but this is not so in the case of HashMap.

Abhijeet Singh · Answer

Sir Please Explain with example?

Vulpes · Answer

The difference is that the LinkedHashMap enables you to iterate through the elements of the map in the order in which they were inserted. In the case of the HashMap class there is no guarantee that this will be the case - the order in which the elements are returned by an iteration will not necessarily be the same as the order in which they were added.