[Java] Restore previous MapVector class names #17879
Description
Making changes to the MapVector class was not part of refactoring plan and should not have been done in ARROW-1710. This will restore class names to the previous state of NullableMapVector -> MapVector -> AbstractMapVector
Reporter: Bryan Cutler / @BryanCutler
Assignee: Bryan Cutler / @BryanCutler
PRs and other links:
Note: This issue was originally created as ARROW-1885. Please see the migration documentation for further details.