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Difference between HashMap and Hashtable | HashMap Vs Hashtable

April 8, 2014 by javainterviewpoint 5 Comments

Both the HashMap and Hashtable implement the interface java.util.Map but there are some slight differences which has to be known to write a much efficient code.

  • The Most important difference between HashMap and the Hashtable is that Hashtable is synchronized and HashMap is non-synchronized , which means Hashtable is thread-safe and can be shared among multiple threads and you don’t need to worry about the synchronization problems. As only one thread can access the Hashtable at a time whereas Hashmap is not thread-safe and it cannot be shared between threads without synchronization. You can synchronize the HashMap using this below code.
Map m = Collections.synchronizedMap(hashMap);
  • HashMap permits one null key and multiple null values whereas the Hashtable will not allow null key or value.
  • Since the Hashtable is thread-safe it is comparatively slower than the HashMap in the environment where Synchronization factor is not considered.
  • HashMap can be traversed by using the iterator, whereas the Hashtable can be traversed by using enumerator and iterator.
  • HashMap inherits AbstractMap class and Hashtable inherits Dictionary class.

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Filed Under: Java, Java Interview Tagged With: difference, hashmap, hashmap and hashtable, hashtable, synchronization, thread-safe

Comments

  1. Deepak says

    September 13, 2016 at 1:20 pm

    Very well explained!!! Thanks 🙂

    Reply
  2. vimal says

    March 25, 2017 at 11:02 pm

    Well Exxplained…

    Reply
  3. Akash says

    May 11, 2017 at 5:36 pm

    Nice one

    Reply
  4. Rajkumar says

    October 11, 2017 at 7:10 pm

    HashMap object capacity is 16 and for HashTable it is 11.

    Reply
  5. Diksha says

    May 13, 2018 at 2:46 am

    Very well explained !

    Reply

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