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😀 Difference between hashmap and hashtable

  • hashtable is synchonized, hashmap is async.

    • synchonized here means get / set is an atomic operation. This means if you have 2 threads trying to get / set value from the hashtable concurrently each operation would be atomic.
  • Hashtable does not allow null keys or values. HashMap allows one null key and any number of null values.

  • hashmap get is O(1) on average but if your hashing function is bad you would be seeing something like O(n)
  • hashmap put is also O(1)

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