title: Is there any reason to have 8 on TREEIFY_THRESHOLD in Java Hashmap?
body: <p>From Java 8, the hashMap modified slightly to have balanced tree instead of linkedlist if more than 8 (TREEIFY_THRESHOLD=8) items on same bucket. is there any reason choosing 8?</p>
  
  <p>would it impact the performance in case it is 9?</p>