Is Java HashMap.clear() and remove() memory effective?

Question

Consider the follwing HashMap.clear() code:

 /**
 * Removes all of the mappings from this map.
 * The map will be empty after this call returns.         


        

Answer 1

Looking at the source code, it does look like HashMap never shrinks. The resize method is called to double the size whenever required, but doesn't have anything ala ArrayList.trimToSize().

If you're using a HashMap in such a way that it grows and shrinks dramatically often, you may want to just create a new HashMap instead of calling clear().