 <p>No, you don't. A quality implementation (<code>Hashtable</code>/<code>HashMap</code>) will resize itself automatically as the number of elements increases.</p> <p>If you are talking about your own implementation, the answer depends on whether the hash table is capable of increasing the number of buckets as its size grows.</p> <p>If you are worried about the performance implications of the resizing, the correct approach is to profile this in the context of your overall application.</p>