[SPARK-19550][BUILD][CORE][WIP] Remove Java 7 support

- Move external/java8-tests tests into core, streaming, sql and remove
- Remove MaxPermGen and related options
- Fix some reflection / TODOs around Java 8+ methods
- Update doc references to 1.7/1.8 differences
- Remove Java 7/8 related build profiles
- Update some plugins for better Java 8 compatibility
- Fix a few Java-related warnings

For the future:

- Update Java 8 examples to fully use Java 8
- Update Java tests to use lambdas for simplicity
- Update Java internal implementations to use lambdas

## How was this patch tested?

Existing tests

Author: Sean Owen <sowen@cloudera.com>

Closes #16871 from srowen/SPARK-19493.

1 files changed, 4 insertions, 2 deletions

diff --git a/docs/index.md b/docs/index.md
index 023e06ada3..19a9d3bfc6 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -26,11 +26,13 @@ Spark runs on both Windows and UNIX-like systems (e.g. Linux, Mac OS). It's easy
 locally on one machine --- all you need is to have `java` installed on your system `PATH`,
 or the `JAVA_HOME` environment variable pointing to a Java installation.
 
-Spark runs on Java 7+, Python 2.6+/3.4+ and R 3.1+. For the Scala API, Spark {{site.SPARK_VERSION}}
+Spark runs on Java 8+, Python 2.6+/3.4+ and R 3.1+. For the Scala API, Spark {{site.SPARK_VERSION}}
 uses Scala {{site.SCALA_BINARY_VERSION}}. You will need to use a compatible Scala version
 ({{site.SCALA_BINARY_VERSION}}.x).
 
-Note that support for Java 7 and Python 2.6 are deprecated as of Spark 2.0.0, and support for 
+Note that support for Java 7 was removed as of Spark 2.2.0.
+
+Note that support for Python 2.6 is deprecated as of Spark 2.0.0, and support for 
 Scala 2.10 and versions of Hadoop before 2.6 are deprecated as of Spark 2.1.0, and may be 
 removed in Spark 2.2.0.