[SPARK-13423][WIP][CORE][SQL][STREAMING] Static analysis fixes for 2.x

## What changes were proposed in this pull request?

Make some cross-cutting code improvements according to static analysis. These are individually up for discussion since they exist in separate commits that can be reverted. The changes are broadly:

- Inner class should be static
- Mismatched hashCode/equals
- Overflow in compareTo
- Unchecked warnings
- Misuse of assert, vs junit.assert
- get(a) + getOrElse(b) -> getOrElse(a,b)
- Array/String .size -> .length (occasionally, -> .isEmpty / .nonEmpty) to avoid implicit conversions
- Dead code
- tailrec
- exists(_ == ) -> contains find + nonEmpty -> exists filter + size -> count
- reduce(_+_) -> sum map + flatten -> map

The most controversial may be .size -> .length simply because of its size. It is intended to avoid implicits that might be expensive in some places.

## How was the this patch tested?

Existing Jenkins unit tests.

Author: Sean Owen <sowen@cloudera.com>

Closes #11292 from srowen/SPARK-13423.

2 files changed, 17 insertions, 20 deletions

diff --git a/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java b/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java
index 0d4c128cb3..ee85626435 100644
--- a/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java
+++ b/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java
@@ -355,27 +355,27 @@ public class JavaDataFrameSuite {
     DataFrame df = context.range(1000);
 
     BloomFilter filter1 = df.stat().bloomFilter("id", 1000, 0.03);
-    assert (filter1.expectedFpp() - 0.03 < 1e-3);
+    Assert.assertTrue(filter1.expectedFpp() - 0.03 < 1e-3);
     for (int i = 0; i < 1000; i++) {
-      assert (filter1.mightContain(i));
+      Assert.assertTrue(filter1.mightContain(i));
     }
 
     BloomFilter filter2 = df.stat().bloomFilter(col("id").multiply(3), 1000, 0.03);
-    assert (filter2.expectedFpp() - 0.03 < 1e-3);
+    Assert.assertTrue(filter2.expectedFpp() - 0.03 < 1e-3);
     for (int i = 0; i < 1000; i++) {
-      assert (filter2.mightContain(i * 3));
+      Assert.assertTrue(filter2.mightContain(i * 3));
     }
 
     BloomFilter filter3 = df.stat().bloomFilter("id", 1000, 64 * 5);
-    assert (filter3.bitSize() == 64 * 5);
+    Assert.assertTrue(filter3.bitSize() == 64 * 5);
     for (int i = 0; i < 1000; i++) {
-      assert (filter3.mightContain(i));
+      Assert.assertTrue(filter3.mightContain(i));
     }
 
     BloomFilter filter4 = df.stat().bloomFilter(col("id").multiply(3), 1000, 64 * 5);
-    assert (filter4.bitSize() == 64 * 5);
+    Assert.assertTrue(filter4.bitSize() == 64 * 5);
     for (int i = 0; i < 1000; i++) {
-      assert (filter4.mightContain(i * 3));
+      Assert.assertTrue(filter4.mightContain(i * 3));
     }
   }
 }
diff --git a/sql/core/src/test/java/test/org/apache/spark/sql/JavaDatasetSuite.java b/sql/core/src/test/java/test/org/apache/spark/sql/JavaDatasetSuite.java
index 1181244c8a..e0e56f3fbf 100644
--- a/sql/core/src/test/java/test/org/apache/spark/sql/JavaDatasetSuite.java
+++ b/sql/core/src/test/java/test/org/apache/spark/sql/JavaDatasetSuite.java
@@ -304,15 +304,12 @@ public class JavaDatasetSuite implements Serializable {
     Assert.assertEquals(Arrays.asList("abc", "abc"), subtracted.collectAsList());
   }
 
-  private <T> Set<T> toSet(List<T> records) {
-    Set<T> set = new HashSet<T>();
-    for (T record : records) {
-      set.add(record);
-    }
-    return set;
+  private static <T> Set<T> toSet(List<T> records) {
+    return new HashSet<>(records);
   }
 
-  private <T> Set<T> asSet(T... records) {
+  @SafeVarargs
+  private static <T> Set<T> asSet(T... records) {
     return toSet(Arrays.asList(records));
   }
 
@@ -529,7 +526,7 @@ public class JavaDatasetSuite implements Serializable {
     Encoders.kryo(PrivateClassTest.class);
   }
 
-  public class SimpleJavaBean implements Serializable {
+  public static class SimpleJavaBean implements Serializable {
     private boolean a;
     private int b;
     private byte[] c;
@@ -612,7 +609,7 @@ public class JavaDatasetSuite implements Serializable {
     }
   }
 
-  public class SimpleJavaBean2 implements Serializable {
+  public static class SimpleJavaBean2 implements Serializable {
     private Timestamp a;
     private Date b;
     private java.math.BigDecimal c;
@@ -650,7 +647,7 @@ public class JavaDatasetSuite implements Serializable {
     }
   }
 
-  public class NestedJavaBean implements Serializable {
+  public static class NestedJavaBean implements Serializable {
     private SimpleJavaBean a;
 
     public SimpleJavaBean getA() {
@@ -745,7 +742,7 @@ public class JavaDatasetSuite implements Serializable {
     ds.collect();
   }
 
-  public class SmallBean implements Serializable {
+  public static class SmallBean implements Serializable {
     private String a;
 
     private int b;
@@ -780,7 +777,7 @@ public class JavaDatasetSuite implements Serializable {
     }
   }
 
-  public class NestedSmallBean implements Serializable {
+  public static class NestedSmallBean implements Serializable {
     private SmallBean f;
 
     public SmallBean getF() {