Hi Sergey, I was also wondering why TreeMap doesn't just use a default comparator and always checks for null instead.
The problem with your patch is that deserialized TreeMap instances which were serialized from a previous version would still have the comparator set to null, thus resulting in a NPE after your patch. And you can't easily fix this because comparator is a final field. Best, Michael On 04.09.2018 21:14, Сергей Цыпанов wrote: > Hi, > > currently (latest code of JDK 11) an instance of TreeMap created with no-arg > contructor has nullable comparator i.e. utilizes no comparator. > > As it comes from the code, a TreeMap created with nullable comparator works > exactly as a TreeMap created with comparator provided by > Comparator.naturalOrder(). This is also explicitly specifid in Javadoc. > > I propose to initialize default comparator of TreeMap with instance of > Comparator returned by Comparator.naturalOrder() instead of null. > This allows to remove the code responsible for handling nullable comparator, > e. g. TreeMap::getEntryUsingComparator can be completely removed in favour of > TreeMap::getEntry. > Similar simplification available for TreeMap::put, TreeMap::compare, > EntrySpliterator::getComparator. > > I've prepared a patch for this. > The patch contains both described major change and some tiny clean-ups e. g. > utilization of Objects::requireNonNull where appropriate and Objects::equals > instead of hand-written TreeMap::valEquals. > > TreeMapTest is green after my changes. > > Regards, > Sergey Tsypanov > >
