arrow

ARROW-8121: [Java] Enhance code style checking for Java code (add spaces after commas, semi-colons and type casts)

This is in response to a discussion in https://github.com/apache/arrow/pull/6039#discussion_r375161992

We found the current style checking for Java code is not sufficient. So we want to enhace it in a series of "small" steps, in order to avoid having to change too many files at once.

In this issue, we add spaces after commas, semi-colons and type casts.

Closes #6622 from liyafan82/fly_0313_style

Authored-by: liyafan82 <fan_li_ya@foxmail.com>
Signed-off-by: Micah Kornfield <emkornfield@gmail.com>