Miscellaneous

1. HashMap make use of Comparable too (since Java 8)
2. WeakHashMap
3. Vector + Enumeration has some bugs -> Iterator is better
4. QuickSort, MergeSort and TimSort
5. Cannot use parallel() with all collections times. TreeSet may block forever.
6. Include the concurrent collections
7. Good collections libraries
   1. https://gist.github.com/kabutz/0fd0efc2c3629e8358d209ba73f0b44e
   2. https://github.com/JCTools/JCTools
   3. https://www.eclipse.org/collections/
   4. https://github.com/OpenHFT/Chronicle-Queue
8. Stream.forEach() vs. Iterable.forEach() - answer