## What changes were proposed in this pull request?

1.0.0 fixes an issue with import order, explicit type for public methods, line length limitation and comment validation:

```
[error] .../spark/repl/scala-2.11/src/main/scala/org/apache/spark/repl/Main.scala:50:16: Are you sure you want to println? If yes, wrap the code block with
[error]       // scalastyle:off println
[error]       println(...)
[error]       // scalastyle:on println
[error] .../spark/repl/scala-2.11/src/main/scala/org/apache/spark/repl/SparkILoop.scala:49: File line length exceeds 100 characters
[error] .../spark/repl/scala-2.11/src/main/scala/org/apache/spark/repl/SparkILoop.scala:22:21: Are you sure you want to println? If yes, wrap the code block with
[error]       // scalastyle:off println
[error]       println(...)
[error]       // scalastyle:on println
[error] .../spark/streaming/src/test/java/org/apache/spark/streaming/JavaTestUtils.scala:35:6: Public method must have explicit type
[error] .../spark/streaming/src/test/java/org/apache/spark/streaming/JavaTestUtils.scala:51:6: Public method must have explicit type
[error] .../spark/streaming/src/test/java/org/apache/spark/streaming/JavaTestUtils.scala:93:15: Public method must have explicit type
[error] .../spark/streaming/src/test/java/org/apache/spark/streaming/JavaTestUtils.scala:98:15: Public method must have explicit type
[error] .../spark/streaming/src/test/java/org/apache/spark/streaming/JavaTestUtils.scala:47:2: Insert a space after the start of the comment
[error] .../spark/streaming/src/test/java/org/apache/spark/streaming/JavaTestUtils.scala:26:43: JavaDStream should come before JavaDStreamLike.
```

This PR also fixes the workaround added in SPARK-16877 for `org.scalastyle.scalariform.OverrideJavaChecker` feature, added from 0.9.0.

## How was this patch tested?

Manually tested.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #19116 from HyukjinKwon/scalastyle-1.0.0.

## What changes were proposed in this pull request?

Add `ThreadUtils.awaitReady` similar to `ThreadUtils.awaitResult` and disallow `Await.ready`.

## How was this patch tested?

Jenkins

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #17763 from zsxwing/awaitready.

## What changes were proposed in this pull request?

Some places in SQL may call `RpcEndpointRef.askWithRetry` (e.g., ParquetFileFormat.buildReader -> SparkContext.broadcast -> ... -> BlockManagerMaster.updateBlockInfo -> RpcEndpointRef.askWithRetry), which will finally call `Await.result`. It may cause `java.lang.IllegalArgumentException: spark.sql.execution.id is already set` when running in Scala ForkJoinPool.

This PR includes the following changes to fix this issue:

- Remove `ThreadUtils.awaitResult`
- Rename `ThreadUtils. awaitResultInForkJoinSafely` to `ThreadUtils.awaitResult`
- Replace `Await.result` in RpcTimeout with `ThreadUtils.awaitResult`.

## How was this patch tested?

Jenkins

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #16230 from zsxwing/fix-SPARK-13747.

## What changes were proposed in this pull request?

This patch significantly improves the performance of event log replay in the HistoryServer via two simple changes:

- **Don't use `extractOpt`**: it turns out that `json4s`'s `extractOpt` method uses exceptions for control flow, causing huge performance bottlenecks due to the overhead of initializing exceptions. To avoid this overhead, we can simply use our own` Utils.jsonOption` method. This patch replaces all uses of `extractOpt` with `Utils.jsonOption` and adds a style checker rule to ban the use of the slow `extractOpt` method.
- **Don't call `Utils.getFormattedClassName` for every event**: the old code called` Utils.getFormattedClassName` dozens of times per replayed event in order to match up class names in events with SparkListener event names. By simply storing the results of these calls in constants rather than recomputing them, we're able to eliminate a huge performance hotspot by removing thousands of expensive `Class.getSimpleName` calls.

## How was this patch tested?

Tested by profiling the replay of a long event log using YourKit. For an event log containing 1000+ jobs, each of which had thousands of tasks, the changes in this patch cut the replay time in half:

![image](https://cloud.githubusercontent.com/assets/50748/19980953/31154622-a1bd-11e6-9be4-21fbb9b3f9a7.png)

Prior to this patch's changes, the two slowest methods in log replay were internal exceptions thrown by `Json4S` and calls to `Class.getSimpleName()`:

![image](https://cloud.githubusercontent.com/assets/50748/19981052/87416cce-a1bd-11e6-9f25-06a7cd391822.png)

After this patch, these hotspots are completely eliminated.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #15756 from JoshRosen/speed-up-jsonprotocol.

## What changes were proposed in this pull request?

Calling `Await.result` will allow other tasks to be run on the same thread when using ForkJoinPool. However, SQL uses a `ThreadLocal` execution id to trace Spark jobs launched by a query, which doesn't work perfectly in ForkJoinPool.

This PR just uses `Awaitable.result` instead to  prevent ForkJoinPool from running other tasks in the current waiting thread.

## How was this patch tested?

Jenkins

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #15520 from zsxwing/SPARK-13747.

## What changes were proposed in this pull request?

This PR adds both rules for preventing to use `Deprecated` and `Override`.

- Java's `Override`
  It seems Scala compiler just ignores this. Apparently, `override` modifier is only mandatory for " that override some other **concrete member definition** in a parent class" but not for for **incomplete member definition** (such as ones from trait or abstract), see (http://www.scala-lang.org/files/archive/spec/2.11/05-classes-and-objects.html#override)

  For a simple example,

  - Normal class - needs `override` modifier

  ```bash
  scala> class A { def say = {}}
  defined class A

  scala> class B extends A { def say = {}}
  <console>:8: error: overriding method say in class A of type => Unit;
   method say needs `override' modifier
         class B extends A { def say = {}}
                                 ^
  ```

  - Trait - does not need `override` modifier

  ```bash
  scala> trait A { def say }
  defined trait A

  scala> class B extends A { def say = {}}
  defined class B
  ```

  To cut this short, this case below is possible,

  ```bash
  scala> class B extends A {
       |    Override
       |    def say = {}
       | }
  defined class B
  ```
  we can write `Override` annotation (meaning nothing) which might confuse engineers that Java's annotation is working fine. It might be great if we prevent those potential confusion.

- Java's `Deprecated`
  When `Deprecated` is used,  it seems Scala compiler recognises this correctly but it seems we use Scala one `deprecated` across codebase.

## How was this patch tested?

Manually tested, by inserting both `Override` and `Deprecated`. This will shows the error messages as below:

```bash
Scalastyle checks failed at following occurrences:
[error] ... : deprecated should be used instead of java.lang.Deprecated.
```

```basg
Scalastyle checks failed at following occurrences:
[error] ... : override modifier should be used instead of java.lang.Override.
```

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #14490 from HyukjinKwon/SPARK-16877.

## What changes were proposed in this pull request?

Replace use of `commons-lang` in favor of `commons-lang3` and forbid the former via scalastyle; remove `NotImplementedException` from `comons-lang` in favor of JDK `UnsupportedOperationException`

## How was this patch tested?

Jenkins tests

Author: Sean Owen <sowen@cloudera.com>

Closes #13843 from srowen/SPARK-16129.

## What changes were proposed in this pull request?

Implement some `hashCode` and `equals` together in order to enable the scalastyle.
This is a first batch, I will continue to implement them but I wanted to know your thoughts.

Author: Joan <joan@goyeau.com>

Closes #12157 from joan38/SPARK-6429-HashCode-Equals.

When `Await.result` throws an exception which originated from a different thread, the resulting stacktrace doesn't include the path leading to the `Await.result` call itself, making it difficult to identify the impact of these exceptions. For example, I've seen cases where broadcast cleaning errors propagate to the main thread and crash it but the resulting stacktrace doesn't include any of the main thread's code, making it difficult to pinpoint which exception crashed that thread.

This patch addresses this issue by explicitly catching, wrapping, and re-throwing exceptions that are thrown by `Await.result`.

I tested this manually using https://github.com/JoshRosen/spark/commit/16b31c825197ee31a50214c6ba3c1df08148f403, a patch which reproduces an issue where an RPC exception which occurs while unpersisting RDDs manages to crash the main thread without any useful stacktrace, and verified that informative, full stacktraces were generated after applying the fix in this PR.

/cc rxin nongli yhuai anabranch

Author: Josh Rosen <joshrosen@databricks.com>

Closes #12433 from JoshRosen/wrap-and-rethrow-await-exceptions.

## What changes were proposed in this pull request?

According to the [Spark Code Style Guide](https://cwiki.apache.org/confluence/display/SPARK/Spark+Code+Style+Guide) and [Scala Style Guide](http://docs.scala-lang.org/style/control-structures.html#curlybraces), we had better enforce the following rule.
  ```
  case: Always omit braces in case clauses.
  ```
This PR makes a new ScalaStyle rule, 'OmitBracesInCase', and enforces it to the code.

## How was this patch tested?

Pass the Jenkins tests (including Scala style checking)

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #12280 from dongjoon-hyun/SPARK-14508.

## What changes were proposed in this pull request?

According to the [Spark Code Style Guide](https://cwiki.apache.org/confluence/display/SPARK/Spark+Code+Style+Guide#SparkCodeStyleGuide-Indentation), this PR adds a new scalastyle rule to prevent the followings.
```
/** In Spark, we don't use the ScalaDoc style so this
  * is not correct.
  */
```

## How was this patch tested?

Pass the Jenkins tests (including `lint-scala`).

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #12221 from dongjoon-hyun/SPARK-14444.

## What changes were proposed in this pull request?

We have ParserUtils and ParseUtils which are both utility collections for use during the parsing process.
Those names and what they are used for is very similar so I think we can merge them.

Also, the original unescapeSQLString method may have a fault. When "\u0061" style character literals are passed to the method, it's not unescaped successfully.
This patch fix the bug.

## How was this patch tested?

Added a new test case.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #12199 from sarutak/merge-ParseUtils-and-ParserUtils.

## What changes were proposed in this pull request?

Since the opening curly brace, '{', has many usages as discussed in [SPARK-3854](https://issues.apache.org/jira/browse/SPARK-3854), this PR adds a ScalaStyle rule to prevent '){' pattern  for the following majority pattern and fixes the code accordingly. If we enforce this in ScalaStyle from now, it will improve the Scala code quality and reduce review time.
```
// Correct:
if (true) {
  println("Wow!")
}

// Incorrect:
if (true){
   println("Wow!")
}
```
IntelliJ also shows new warnings based on this.

## How was this patch tested?

Pass the Jenkins ScalaStyle test.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #11637 from dongjoon-hyun/SPARK-3854.

andrewor14
Please take a look

Author: tedyu <yuzhihong@gmail.com>

Closes #11134 from tedyu/master.

This is the final PR about SPARK-12692.
We have removed all of white spaces before comma from code so let's enforce style checking.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #10736 from sarutak/SPARK-12692-followup-enforce-checking.

Fix the style violation (space before , and :).
This PR is a followup for #10643

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #10719 from sarutak/SPARK-12692-followup-core.

This reverts commit 8cfa218f.

Fix the style violation (space before , and :).
This PR is a followup for #10643.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #10718 from sarutak/SPARK-12692-followup-sql.

Turn import ordering violations into build errors, plus a few adjustments
to account for how the checker behaves. I'm a little on the fence about
whether the existing code is right, but it's easier to appease the checker
than to discuss what's the more correct order here.

Plus a few fixes to imports that cropped in since my recent cleanups.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #10612 from vanzin/SPARK-3873-enable.

We should not put a white space before `,` and `:` so let's check it.
Because there are lots of style violations, first, I'd like to add a checker, enable and let the level `warning`.
Then, I'd like to fix the style step by step.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #10643 from sarutak/SPARK-12692.

[SPARK-12481][CORE][STREAMING][SQL] Remove usage of Hadoop deprecated APIs and reflection that supported 1.x

Remove use of deprecated Hadoop APIs now that 2.2+ is required

Author: Sean Owen <sowen@cloudera.com>

Closes #10446 from srowen/SPARK-12481.

A slight adjustment to the checker configuration was needed; there is
a handful of warnings still left, but those are because of a bug in
the checker that I'll fix separately (before enabling errors for the
checker, of course).

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #10535 from vanzin/SPARK-3873-mllib.

SPARK-9886 fixed ExternalBlockStore.scala

This PR fixes the remaining references to Runtime.getRuntime.addShutdownHook()

Author: tedyu <yuzhihong@gmail.com>

Closes #10325 from ted-yu/master.

The checker tries to follow as closely as possible the guidelines of
the code style document, and makes some decisions where the guide is
not clear. In particular:

- wildcard imports come first when there are other imports in the
  same package
- multi-import blocks come before single imports
- lower-case names inside multi-import blocks come before others

In some projects, such as graphx, there seems to be a convention to
separate o.a.s imports from the project's own; to simplify the
checker, I chose not to allow that, which is a strict interpretation
of the code style guide, even though I think it makes sense.

Since the checks are based on syntax only, some edge cases may
generate spurious warnings; for example, when class names start
with a lower case letter (and are thus treated as a package name
by the checker).

The checker is currently only generating warnings, and since there
are many of those, the build output does get a little noisy. The
idea is to fix the code (and the checker, as needed) little by little
instead of having a huge change that touches everywhere.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #6502 from vanzin/SPARK-3873.

See http://search-hadoop.com/m/q3RTtjpe8r1iRbTj2 for discussion.

Summary: addition of VisibleForTesting annotation resulted in spark-shell malfunctioning.

Author: tedyu <yuzhihong@gmail.com>

Closes #9585 from tedyu/master.

This is a followup to #8499 which adds a Scalastyle rule to mandate the use of SparkHadoopUtil's JobContext accessor methods and fixes the existing violations.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #8521 from JoshRosen/SPARK-10330-part2.

Replace `JavaConversions` implicits with `JavaConverters`

Most occurrences I've seen so far are necessary conversions; a few have been avoidable. None are in critical code as far as I see, yet.

Author: Sean Owen <sowen@cloudera.com>

Closes #8033 from srowen/SPARK-9613.

This pull request adds a Scalastyle regex rule which fails the style check if `Class.forName` is used directly.  `Class.forName` always loads classes from the default / system classloader, but in a majority of cases, we should be using Spark's own `Utils.classForName` instead, which tries to load classes from the current thread's context classloader and falls back to the classloader which loaded Spark when the context classloader is not defined.

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/apache/spark/7350)
<!-- Reviewable:end -->

Author: Josh Rosen <joshrosen@databricks.com>

Closes #7350 from JoshRosen/ban-Class.forName and squashes the following commits:

e3e96f7 [Josh Rosen] Merge remote-tracking branch 'origin/master' into ban-Class.forName
c0b7885 [Josh Rosen] Hopefully fix the last two cases
d707ba7 [Josh Rosen] Fix uses of Class.forName that I missed in my first cleanup pass
046470d [Josh Rosen] Merge remote-tracking branch 'origin/master' into ban-Class.forName
62882ee [Josh Rosen] Fix uses of Class.forName or add exclusion.
d9abade [Josh Rosen] Add stylechecker rule to ban uses of Class.forName

Author: Jonathan Alter <jonalter@users.noreply.github.com>

Closes #7093 from jonalter/SPARK-7977 and squashes the following commits:

ccd44cc [Jonathan Alter] Changed println to log in ThreadingSuite
7fcac3e [Jonathan Alter] Reverting to println in ThreadingSuite
10724b6 [Jonathan Alter] Changing some printlns to logs in tests
eeec1e7 [Jonathan Alter] Merge branch 'master' of github.com:apache/spark into SPARK-7977
0b1dcb4 [Jonathan Alter] More println cleanup
aedaf80 [Jonathan Alter] Merge branch 'master' of github.com:apache/spark into SPARK-7977
925fd98 [Jonathan Alter] Merge branch 'master' of github.com:apache/spark into SPARK-7977
0c16fa3 [Jonathan Alter] Replacing some printlns with logs
45c7e05 [Jonathan Alter] Merge branch 'master' of github.com:apache/spark into SPARK-7977
5c8e283 [Jonathan Alter] Allowing println in audit-release examples
5b50da1 [Jonathan Alter] Allowing printlns in example files
ca4b477 [Jonathan Alter] Merge branch 'master' of github.com:apache/spark into SPARK-7977
83ab635 [Jonathan Alter] Fixing new printlns
54b131f [Jonathan Alter] Merge branch 'master' of github.com:apache/spark into SPARK-7977
1cd8a81 [Jonathan Alter] Removing some unnecessary comments and printlns
b837c3a [Jonathan Alter] Disallowing println

(1) rules that we enforce.
(2) rules that we would like to enforce, but haven't cleaned up the codebase to
    turn on yet (or we need to make the scalastyle rule more configurable).
(3) rules that we don't want to enforce.

Author: Reynold Xin <rxin@databricks.com>

Closes #6543 from rxin/scalastyle and squashes the following commits:

beefaab [Reynold Xin] [SPARK-7986] Split scalastyle config into 3 sections.

Author: Reynold Xin <rxin@databricks.com>

Closes #6541 from rxin/trailing-whitespace-on and squashes the following commits:

f72ebe4 [Reynold Xin] [SPARK-3850] Turn style checker on for trailing whitespaces.

Author: Reynold Xin <rxin@databricks.com>

Closes #6536 from rxin/structural-type-checker and squashes the following commits:

f833151 [Reynold Xin] Fixed compilation.
633f9a1 [Reynold Xin] Fixed typo.
d1fa804 [Reynold Xin] [SPARK-7979] Enforce structural type checker.

Author: Reynold Xin <rxin@databricks.com>

This patch had conflicts when merged, resolved by
Committer: Reynold Xin <rxin@databricks.com>

Closes #6527 from rxin/covariant-equals and squashes the following commits:

e7d7784 [Reynold Xin] [SPARK-7975] Enforce CovariantEqualsChecker

Author: Reynold Xin <rxin@databricks.com>

Closes #6528 from rxin/style-finalizer and squashes the following commits:

a2211ca [Reynold Xin] [SPARK-7976] Enable NoFinalizeChecker.

This is a follow-up patch to #6441.

Author: Andrew Or <andrew@databricks.com>

Closes #6510 from andrewor14/extends-funsuite-check and squashes the following commits:

6618b46 [Andrew Or] Exempt SparkSinkSuite from the FunSuite check
99d02ac [Andrew Or] Merge branch 'master' of github.com:apache/spark into extends-funsuite-check
48874dd [Andrew Or] Guard against direct uses of FunSuite / FunSuiteLike

[SPARK-7940] Enforce whitespace checking for DO, TRY, CATCH, FINALLY, MATCH, LARROW, RARROW in style checker.

…

Author: Reynold Xin <rxin@databricks.com>

Closes #6491 from rxin/more-whitespace and squashes the following commits:

f6e63dc [Reynold Xin] [SPARK-7940] Enforce whitespace checking for DO, TRY, CATCH, FINALLY, MATCH, LARROW, RARROW in style checker.

This is the last batch of changes to complete SPARK-7929.

Previous related PRs:
https://github.com/apache/spark/pull/6480
https://github.com/apache/spark/pull/6478
https://github.com/apache/spark/pull/6477
https://github.com/apache/spark/pull/6476
https://github.com/apache/spark/pull/6475
https://github.com/apache/spark/pull/6474
https://github.com/apache/spark/pull/6473

Author: Reynold Xin <rxin@databricks.com>

Closes #6487 from rxin/whitespace-lint and squashes the following commits:

b33d43d [Reynold Xin] [SPARK-7929] Turn whitespace checker on for more token types.

This builds on my earlier pull requests and turns on the explicit type checking in scalastyle.

Author: Reynold Xin <rxin@databricks.com>

Closes #5342 from rxin/SPARK-6428 and squashes the following commits:

7b531ab [Reynold Xin] import ordering
2d9a8a5 [Reynold Xin] jl
e668b1c [Reynold Xin] override
9b9e119 [Reynold Xin] Parenthesis.
82e0cf5 [Reynold Xin] [SPARK-6428] Turn on explicit type checking for public methods.

Author: Reynold Xin <rxin@databricks.com>

Closes #5125 from rxin/core-explicit-type and squashes the following commits:

f471415 [Reynold Xin] Revert style checker changes.
81b66e4 [Reynold Xin] Code review feedback.
a7533e3 [Reynold Xin] Mima excludes.
1d795f5 [Reynold Xin] [SPARK-6428] Added explicit types for all public methods in core.