title: Forcing deallocation of large cache object in Java
body: <p>I use a large (millions) entries hashmap to cache values needed by an algorithm, the key is a combination of two objects as a long. Since it grows continuously (because keys in the map changes, so old ones are not needed anymore) it would be nice to be able to force wiping all the data contained in it and start again during the execution, is there a way to do effectively in Java?</p>
  
  <p>I mean release the associated memory (about 1-1.5gb of hashmap) and restart from the empty hashmap..</p>