[Java] Provide a flag to enable/disable null-checking in vectors' get methods

[asfimport]

For vector classes, the get method first checks if the value at the given index is null. If it is not null, the method goes ahead to retrieve the value.
For some scenarios, the first check is redundant, because the application code has already checked the null, before calling the get method. This redundant check may have non-trivial performance overheads.

So we add a flag to enable/disable the null checking, so the user can set the flag according to their own specific scenario.

Reporter: Liya Fan / @liyafan82
Assignee: Liya Fan / @liyafan82

Related issues:

• [Java] Provide light-weight arrow APIs (relates to)

PRs and other links:

• GitHub Pull Request #4288

_{Note: This issue was originally created as ARROW-5290. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 4288
#4288