[SPARK-10547] [TEST] Streamline / improve style of Java API tests

[srowen]

Fix a few Java API test style issues: unused generic types, exceptions, wrong assert argument order

[SparkQA]

Test build #42290 has finished for PR 8706 at commit 3ecaf9f.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • static class Converter implements Function<InputStream, Iterable<String>>
  • static class JavaSocketReceiver extends Receiver<String>

[vanzin]

This looks a little odd since it mixes two different indentation / alignment styles. In these cases I tend to prefer something like this:

Assert.assertEquals(partitions.get(0),
  Arrays.asList(new Tuple2<>(0, 5), new Tuple2<>(0, 8), new Tuple2<>(2, 6)));

[vanzin]

LGTM, just minor things. Not super sold on the alignment style (seems most of existing code does it differently), but don't really care either way.

[srowen]

All the rest of the comments look good and I've implemented them in the next push. There's no good answer on some of these indentations, but I tried to standardize it more towards line break and deep 4-space indents.

[SparkQA]

Test build #42328 has finished for PR 8706 at commit e6524b8.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #1742 has finished for PR 8706 at commit e6524b8.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.