[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.

2 files changed, 3 insertions, 3 deletions

diff --git a/examples/src/main/java/org/apache/spark/examples/ml/JavaTokenizerExample.java b/examples/src/main/java/org/apache/spark/examples/ml/JavaTokenizerExample.java
index f42fd3317b..004e9b12f6 100644
--- a/examples/src/main/java/org/apache/spark/examples/ml/JavaTokenizerExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/ml/JavaTokenizerExample.java
@@ -69,9 +69,9 @@ public class JavaTokenizerExample {
         .setOutputCol("words")
         .setPattern("\\W");  // alternatively .setPattern("\\w+").setGaps(false);
 
-    spark.udf().register("countTokens", new UDF1<WrappedArray, Integer>() {
+    spark.udf().register("countTokens", new UDF1<WrappedArray<String>, Integer>() {
       @Override
-      public Integer call(WrappedArray words) {
+      public Integer call(WrappedArray<String> words) {
         return words.size();
       }
     }, DataTypes.IntegerType);
diff --git a/examples/src/main/java/org/apache/spark/examples/sql/JavaSQLDataSourceExample.java b/examples/src/main/java/org/apache/spark/examples/sql/JavaSQLDataSourceExample.java
index 1860594e8e..b687fae5a1 100644
--- a/examples/src/main/java/org/apache/spark/examples/sql/JavaSQLDataSourceExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/sql/JavaSQLDataSourceExample.java
@@ -224,7 +224,7 @@ public class JavaSQLDataSourceExample {
             "{\"name\":\"Yin\",\"address\":{\"city\":\"Columbus\",\"state\":\"Ohio\"}}");
     JavaRDD<String> anotherPeopleRDD =
             new JavaSparkContext(spark.sparkContext()).parallelize(jsonData);
-    Dataset anotherPeople = spark.read().json(anotherPeopleRDD);
+    Dataset<Row> anotherPeople = spark.read().json(anotherPeopleRDD);
     anotherPeople.show();
     // +---------------+----+
     // |        address|name|