CodeStyle formatting to conform to basic Checkstyle rules.

[bvaradar]

This diff contains formatting changes to adhere to basic checkstyle rules (conforming to google-format).

I am adding the checkstyle and corresponding eclipse/IntelliJ code-styles under "style/" folder so that all of us can use the same ide code-styles. I have made few changes to google-format checkstyle:

1. Increase line length from 100 to 120
2. Comment out JavaDoc related checkstyles as this needs more manual work.

I have added 2 files to checkstyle suppressions list (style/checkstyle-suppressions.xml). One of them was because of checkstyle bug. Please keep in mind that checkstyle is somewhat of a super-set compared to code-styles when it comes to enforcing rules.

With the maven settings, now "mvn compile" will fail if there are any checkstyle violations.

Major theme in the below diff as suggested by checkstyle:

1. Line limit to 120
2. Lambda Expression Indentation (Please note that IntelliJ does not have good support for this. In some cases, we need to manually indent).
3. Moving top-level non-public classes to separate files
4. Using default (in switch) to cover bases.
5. Modifier Ordering (final static vs static final)
6. Local Variable Naming

[n3nash]

@jianxu FYI since this might cause merging/syncing with internal repo.

[jianxu]

thanks @n3nash! @bvaradar is there way to apply the coding style change without manually indent for some cases?

[bvaradar]

@jianxu : Other than multi-line lambda expressions and very deep-nested generics based expressions, the indentations should work automatically if you use the style/intellij-java-google-style.xml (in this PR) as code-style (for intellij) and do Reformat-Code.

For IntelliJ Ultimate 2017.3, the way to setupis Preferences -> Editor -> Code Style -> Java -> Import Schema (under Settings icon) -> IntelliJ IDEA Code Style XML

[jianxu]

@bvaradar Thanks for the info, maybe also update https://github.com/uber/hudi/blob/master/docs/dev_setup.md ?

[bvaradar]

Thanks @jianxu. I have updated the doc.

[n3nash]

@bvaradar it LGTM. Can you hold off on merging this till I merge the 1 large PR I have. I would like to avoid dealing with conflicts if possible, thanks

[n3nash]

Is this supposed to be there by default ?

@bvaradar

[bvaradar]

Yes @n3nash , https://github.com/google/styleguide/blob/gh-pages/intellij-java-google-style.xml

[vinothchandar]

Just confirming, you have brought checkstyle formatting and the intellij formatting in sync, correct?

As long as one sets up IDE with the checked in style, it should all be fine?

[bvaradar]

@vinothchandar : Both specifications are aligned to the extent they are not contradicting each other. But there are some exceptions.

1. there is an issue with checkstyle causing a generic indentation rule to fail for some nested lambda expressions (have added suppression for one case).
2. There are below caveats as I could not express some checkstyle rules in code-style (but felt should be good to have). They are:
   (a) Moving top-level non-public classes to separate files
   (b) Using default in switch
   (c) Local Variables Naming

[vinothchandar]

sg.. can you rebase this once #350 is merged.. I think this is what @n3nash is hinting at.

[vinothchandar]

@n3nash can @bvaradar merge this now? @bvaradar please rebase this based off latest master since a few commits have a gone in..

[vinothchandar]

@jianxu any concerns before I merge this? @n3nash ?

[n3nash]

@vinothchandar No objections from my end. @bvaradar BTW, does this take care of unused imports too ?

[bvaradar]

@n3nash : Thanks. Added both Unused and Redundant Imports in checkstyle and corresponding code-style. If there are any other rules missing, we can add them in future PRs.

[jianxu]

@vinothchandar @bvaradar sounds good to me. Let's also make sure all pending PRs are rebased after this change is merged.

cc @kaushikd49 @ovj please try to rebase your changes on top of this PR and also setup your IDEs correspondingly.