Improve `collection` related things that reusing a immutable object instead of creating a new object (#4135)

api/src/test/java/io/druid/data/input/impl/CSVParseSpecTest.java

@@ -23,6 +23,7 @@ import com.google.common.collect.Lists;
 import org.junit.Test;
 
 import java.util.Arrays;
+import java.util.Collections;
 
 public class CSVParseSpecTest
 {
@@ -41,7 +42,7 @@ public class CSVParseSpecTest
             Lists.<SpatialDimensionSchema>newArrayList()
         ),
         ",",
-        Arrays.asList("a"),
+        Collections.singletonList("a"),
         false,
         0
     );
@@ -62,7 +63,7 @@ public class CSVParseSpecTest
             Lists.<SpatialDimensionSchema>newArrayList()
         ),
         ",",
-        Arrays.asList("a"),
+        Collections.singletonList("a"),
         false,
         0
     );

api/src/test/java/io/druid/data/input/impl/DelimitedParseSpecTest.java

@@ -27,6 +27,7 @@ import org.junit.Test;
 
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Collections;
 
 public class DelimitedParseSpecTest
 {
@@ -37,10 +38,10 @@ public class DelimitedParseSpecTest
   {
     DelimitedParseSpec spec = new DelimitedParseSpec(
         new TimestampSpec("abc", "iso", null),
-        new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Arrays.asList("abc")), null, null),
+        new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Collections.singletonList("abc")), null, null),
         "\u0001",
         "\u0002",
-        Arrays.asList("abc"),
+        Collections.singletonList("abc"),
         false,
         0
     );
@@ -51,10 +52,10 @@ public class DelimitedParseSpecTest
     Assert.assertEquals("abc", serde.getTimestampSpec().getTimestampColumn());
     Assert.assertEquals("iso", serde.getTimestampSpec().getTimestampFormat());
 
-    Assert.assertEquals(Arrays.asList("abc"), serde.getColumns());
+    Assert.assertEquals(Collections.singletonList("abc"), serde.getColumns());
     Assert.assertEquals("\u0001", serde.getDelimiter());
     Assert.assertEquals("\u0002", serde.getListDelimiter());
-    Assert.assertEquals(Arrays.asList("abc"), serde.getDimensionsSpec().getDimensionNames());
+    Assert.assertEquals(Collections.singletonList("abc"), serde.getDimensionsSpec().getDimensionNames());
   }
 
   @Test(expected = IllegalArgumentException.class)
@@ -73,7 +74,7 @@ public class DelimitedParseSpecTest
         ),
         ",",
         " ",
-        Arrays.asList("a"),
+        Collections.singletonList("a"),
         false,
         0
     );
@@ -95,7 +96,7 @@ public class DelimitedParseSpecTest
         ),
         ",",
         null,
-        Arrays.asList("a"),
+        Collections.singletonList("a"),
         false,
         0
     );

api/src/test/java/io/druid/data/input/impl/JavaScriptParseSpecTest.java

@@ -22,7 +22,6 @@ package io.druid.data.input.impl;
 import com.fasterxml.jackson.databind.InjectableValues;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.collect.ImmutableMap;
-
 import io.druid.TestObjectMapper;
 import io.druid.java.util.common.parsers.Parser;
 import io.druid.js.JavaScriptConfig;
@@ -32,7 +31,7 @@ import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
 import java.io.IOException;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.Map;
 
 /**
@@ -55,7 +54,7 @@ public class JavaScriptParseSpecTest
     );
     JavaScriptParseSpec spec = new JavaScriptParseSpec(
         new TimestampSpec("abc", "iso", null),
-        new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Arrays.asList("abc")), null, null),
+        new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Collections.singletonList("abc")), null, null),
         "abc",
         JavaScriptConfig.getEnabledInstance()
     );
@@ -67,7 +66,7 @@ public class JavaScriptParseSpecTest
     Assert.assertEquals("iso", serde.getTimestampSpec().getTimestampFormat());
 
     Assert.assertEquals("abc", serde.getFunction());
-    Assert.assertEquals(Arrays.asList("abc"), serde.getDimensionsSpec().getDimensionNames());
+    Assert.assertEquals(Collections.singletonList("abc"), serde.getDimensionsSpec().getDimensionNames());
   }
 
   @Test
@@ -76,7 +75,7 @@ public class JavaScriptParseSpecTest
     final JavaScriptConfig config = JavaScriptConfig.getEnabledInstance();
     JavaScriptParseSpec spec = new JavaScriptParseSpec(
         new TimestampSpec("abc", "iso", null),
-        new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Arrays.asList("abc")), null, null),
+        new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Collections.singletonList("abc")), null, null),
         "function(str) { var parts = str.split(\"-\"); return { one: parts[0], two: parts[1] } }",
         config
     );
@@ -92,7 +91,7 @@ public class JavaScriptParseSpecTest
     final JavaScriptConfig config = new JavaScriptConfig(false);
     JavaScriptParseSpec spec = new JavaScriptParseSpec(
         new TimestampSpec("abc", "iso", null),
-        new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Arrays.asList("abc")), null, null),
+        new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Collections.singletonList("abc")), null, null),
         "abc",
         config
     );

api/src/test/java/io/druid/data/input/impl/ParseSpecTest.java

@@ -26,6 +26,7 @@ import io.druid.java.util.common.parsers.ParseException;
 import org.junit.Test;
 
 import java.util.Arrays;
+import java.util.Collections;
 
 public class ParseSpecTest
 {
@@ -83,7 +84,7 @@ public class ParseSpecTest
             null
         ),
         new DimensionsSpec(
-            DimensionsSpec.getDefaultSchemas(Arrays.asList("a")),
+            DimensionsSpec.getDefaultSchemas(Collections.singletonList("a")),
             Lists.newArrayList("B", "B"),
             Lists.<SpatialDimensionSchema>newArrayList()
         ),

api/src/test/java/io/druid/data/input/impl/RegexParseSpecTest.java

@@ -25,7 +25,7 @@ import org.junit.Assert;
 import org.junit.Test;
 
 import java.io.IOException;
-import java.util.Arrays;
+import java.util.Collections;
 
 /**
  */
@@ -38,9 +38,9 @@ public class RegexParseSpecTest
   {
     RegexParseSpec spec = new RegexParseSpec(
         new TimestampSpec("abc", "iso", null),
-        new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Arrays.asList("abc")), null, null),
+        new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Collections.singletonList("abc")), null, null),
         "\u0001",
-        Arrays.asList("abc"),
+        Collections.singletonList("abc"),
         "abc"
     );
     final RegexParseSpec serde = jsonMapper.readValue(
@@ -52,6 +52,6 @@ public class RegexParseSpecTest
 
     Assert.assertEquals("abc", serde.getPattern());
     Assert.assertEquals("\u0001", serde.getListDelimiter());
-    Assert.assertEquals(Arrays.asList("abc"), serde.getDimensionsSpec().getDimensionNames());
+    Assert.assertEquals(Collections.singletonList("abc"), serde.getDimensionsSpec().getDimensionNames());
   }
 }

api/src/test/java/io/druid/guice/PolyBindTest.java

@@ -32,6 +32,7 @@ import org.junit.Assert;
 import org.junit.Test;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Properties;
 
 /**
@@ -46,7 +47,7 @@ public class PolyBindTest
     props = new Properties();
     injector = Guice.createInjector(
         Iterables.concat(
-            Arrays.asList(
+            Collections.singletonList(
                 new Module()
                 {
                   @Override

benchmarks/src/main/java/io/druid/benchmark/FilteredAggregatorBenchmark.java

@@ -95,6 +95,7 @@ import java.io.File;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 
@@ -128,7 +129,11 @@ public class FilteredAggregatorBenchmark
   private File tmpDir;
 
   private static String JS_FN = "function(str) { return 'super-' + str; }";
-  private static ExtractionFn JS_EXTRACTION_FN = new JavaScriptExtractionFn(JS_FN, false, JavaScriptConfig.getEnabledInstance());
+  private static ExtractionFn JS_EXTRACTION_FN = new JavaScriptExtractionFn(
+      JS_FN,
+      false,
+      JavaScriptConfig.getEnabledInstance()
+  );
 
   static {
     JSON_MAPPER = new DefaultObjectMapper();
@@ -169,10 +174,15 @@ public class FilteredAggregatorBenchmark
     filter = new OrDimFilter(
         Arrays.asList(
             new BoundDimFilter("dimSequential", "-1", "-1", true, true, null, null, StringComparators.ALPHANUMERIC),
-            new JavaScriptDimFilter("dimSequential", "function(x) { return false }", null, JavaScriptConfig.getEnabledInstance()),
+            new JavaScriptDimFilter(
+                "dimSequential",
+                "function(x) { return false }",
+                null,
+                JavaScriptConfig.getEnabledInstance()
+            ),
             new RegexDimFilter("dimSequential", "X", null),
             new SearchQueryDimFilter("dimSequential", new ContainsSearchQuerySpec("X", false), null),
-            new InDimFilter("dimSequential", Arrays.asList("X"), null)
+            new InDimFilter("dimSequential", Collections.singletonList("X"), null)
         )
     );
     filteredMetrics = new AggregatorFactory[1];
@@ -208,7 +218,7 @@ public class FilteredAggregatorBenchmark
     );
 
     BenchmarkSchemaInfo basicSchema = BenchmarkSchemas.SCHEMA_MAP.get("basic");
-    QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+    QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
     List<AggregatorFactory> queryAggs = new ArrayList<>();
     queryAggs.add(filteredMetrics[0]);
 

benchmarks/src/main/java/io/druid/benchmark/GroupByTypeInterfaceBenchmark.java

@@ -96,7 +96,7 @@ import java.io.File;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -174,7 +174,7 @@ public class GroupByTypeInterfaceBenchmark
     BenchmarkSchemaInfo basicSchema = BenchmarkSchemas.SCHEMA_MAP.get("basic");
 
     { // basic.A
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory(
           "sumLongSequential",
@@ -240,7 +240,7 @@ public class GroupByTypeInterfaceBenchmark
     }
 
     { // basic.nested
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory(
           "sumLongSequential",

benchmarks/src/main/java/io/druid/benchmark/TopNTypeInterfaceBenchmark.java

@@ -89,7 +89,7 @@ import org.openjdk.jmh.infra.Blackhole;
 import java.io.File;
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -159,7 +159,7 @@ public class TopNTypeInterfaceBenchmark
     BenchmarkSchemaInfo basicSchema = BenchmarkSchemas.SCHEMA_MAP.get("basic");
 
     { // basic.A
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory("sumLongSequential", "sumLongSequential"));
@@ -199,7 +199,7 @@ public class TopNTypeInterfaceBenchmark
       basicQueries.put("float", queryBuilderFloat);
     }
     { // basic.numericSort
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory("sumLongSequential", "sumLongSequential"));
@@ -215,7 +215,7 @@ public class TopNTypeInterfaceBenchmark
       basicQueries.put("numericSort", queryBuilderA);
     }
     { // basic.alphanumericSort
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory("sumLongSequential", "sumLongSequential"));

benchmarks/src/main/java/io/druid/benchmark/datagen/SequentialDistribution.java

@@ -22,7 +22,7 @@ package io.druid.benchmark.datagen;
 import org.apache.commons.math3.distribution.EnumeratedDistribution;
 import org.apache.commons.math3.util.Pair;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 public class SequentialDistribution extends EnumeratedDistribution
@@ -37,7 +37,7 @@ public class SequentialDistribution extends EnumeratedDistribution
   public SequentialDistribution(Integer start, Integer end, List<Object> enumeratedValues)
   {
     // just pass in some bogus probability mass function, we won't be using it
-    super(Arrays.asList(new Pair<Object, Double>(null, 1.0)));
+    super(Collections.singletonList(new Pair<Object, Double>(null, 1.0)));
     this.start = start;
     this.end = end;
     this.enumeratedValues = enumeratedValues;

benchmarks/src/main/java/io/druid/benchmark/indexing/IncrementalIndexReadBenchmark.java

@@ -67,6 +67,7 @@ import org.openjdk.jmh.infra.Blackhole;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 
@@ -173,7 +174,7 @@ public class IncrementalIndexReadBenchmark
             new JavaScriptDimFilter("dimSequential", "function(x) { return false }", null, JavaScriptConfig.getEnabledInstance()),
             new RegexDimFilter("dimSequential", "X", null),
             new SearchQueryDimFilter("dimSequential", new ContainsSearchQuerySpec("X", false), null),
-            new InDimFilter("dimSequential", Arrays.asList("X"), null)
+            new InDimFilter("dimSequential", Collections.singletonList("X"), null)
         )
     );
 

benchmarks/src/main/java/io/druid/benchmark/query/GroupByBenchmark.java

@@ -98,7 +98,7 @@ import java.io.File;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -174,7 +174,7 @@ public class GroupByBenchmark
     BenchmarkSchemaInfo basicSchema = BenchmarkSchemas.SCHEMA_MAP.get("basic");
 
     { // basic.A
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory(
           "sumLongSequential",
@@ -202,7 +202,7 @@ public class GroupByBenchmark
     }
 
     { // basic.nested
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory(
           "sumLongSequential",
@@ -246,7 +246,7 @@ public class GroupByBenchmark
     BenchmarkSchemaInfo simpleSchema = BenchmarkSchemas.SCHEMA_MAP.get("simple");
 
     { // simple.A
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(simpleSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(simpleSchema.getDataInterval()));
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory(
           "rows",
@@ -273,7 +273,7 @@ public class GroupByBenchmark
     Map<String, GroupByQuery> simpleLongQueries = new LinkedHashMap<>();
     BenchmarkSchemaInfo simpleLongSchema = BenchmarkSchemas.SCHEMA_MAP.get("simpleLong");
     { // simpleLong.A
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(simpleLongSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(simpleLongSchema.getDataInterval()));
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory(
           "rows",
@@ -300,7 +300,7 @@ public class GroupByBenchmark
     Map<String, GroupByQuery> simpleFloatQueries = new LinkedHashMap<>();
     BenchmarkSchemaInfo simpleFloatSchema = BenchmarkSchemas.SCHEMA_MAP.get("simpleFloat");
     { // simpleFloat.A
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(simpleFloatSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(simpleFloatSchema.getDataInterval()));
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory(
           "rows",

benchmarks/src/main/java/io/druid/benchmark/query/SearchBenchmark.java

@@ -97,7 +97,7 @@ import org.openjdk.jmh.infra.Blackhole;
 import java.io.File;
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -188,7 +188,7 @@ public class SearchBenchmark
 
   private static SearchQueryBuilder basicA(final BenchmarkSchemaInfo basicSchema)
   {
-    final QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+    final QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
     return Druids.newSearchQueryBuilder()
                  .dataSource("blah")
@@ -199,7 +199,7 @@ public class SearchBenchmark
 
   private static SearchQueryBuilder basicB(final BenchmarkSchemaInfo basicSchema)
   {
-    final QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+    final QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
     final List<String> dimUniformFilterVals = Lists.newArrayList();
     int resultNum = (int) (100000 * 0.1);
@@ -230,7 +230,7 @@ public class SearchBenchmark
 
   private static SearchQueryBuilder basicC(final BenchmarkSchemaInfo basicSchema)
   {
-    final QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+    final QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
     final List<String> dimUniformFilterVals = Lists.newArrayList();
     final int resultNum = (int) (100000 * 0.1);
@@ -284,7 +284,7 @@ public class SearchBenchmark
 
   private static SearchQueryBuilder basicD(final BenchmarkSchemaInfo basicSchema)
   {
-    final QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+    final QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
     final List<String> dimUniformFilterVals = Lists.newArrayList();
     final int resultNum = (int) (100000 * 0.1);

benchmarks/src/main/java/io/druid/benchmark/query/SelectBenchmark.java

@@ -88,6 +88,7 @@ import java.io.File;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -156,7 +157,7 @@ public class SelectBenchmark
     BenchmarkSchemaInfo basicSchema = BenchmarkSchemas.SCHEMA_MAP.get("basic");
 
     { // basic.A
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
       Druids.SelectQueryBuilder queryBuilderA =
           Druids.newSelectQueryBuilder()

benchmarks/src/main/java/io/druid/benchmark/query/TimeseriesBenchmark.java

@@ -92,7 +92,7 @@ import org.openjdk.jmh.infra.Blackhole;
 import java.io.File;
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -155,7 +155,7 @@ public class TimeseriesBenchmark
     BenchmarkSchemaInfo basicSchema = BenchmarkSchemas.SCHEMA_MAP.get("basic");
 
     { // basic.A
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory("sumLongSequential", "sumLongSequential"));
@@ -176,7 +176,7 @@ public class TimeseriesBenchmark
       basicQueries.put("A", queryA);
     }
     {
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       LongSumAggregatorFactory lsaf = new LongSumAggregatorFactory("sumLongSequential", "sumLongSequential");
@@ -196,7 +196,7 @@ public class TimeseriesBenchmark
       basicQueries.put("timeFilterNumeric", timeFilterQuery);
     }
     {
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       LongSumAggregatorFactory lsaf = new LongSumAggregatorFactory("sumLongSequential", "sumLongSequential");
@@ -216,7 +216,7 @@ public class TimeseriesBenchmark
       basicQueries.put("timeFilterAlphanumeric", timeFilterQuery);
     }
     {
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(new Interval(200000, 300000)));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(new Interval(200000, 300000)));
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       LongSumAggregatorFactory lsaf = new LongSumAggregatorFactory("sumLongSequential", "sumLongSequential");
       queryAggs.add(lsaf);

benchmarks/src/main/java/io/druid/benchmark/query/TopNBenchmark.java

@@ -89,7 +89,7 @@ import org.openjdk.jmh.infra.Blackhole;
 import java.io.File;
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -156,7 +156,7 @@ public class TopNBenchmark
     BenchmarkSchemaInfo basicSchema = BenchmarkSchemas.SCHEMA_MAP.get("basic");
 
     { // basic.A
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory("sumLongSequential", "sumLongSequential"));
@@ -176,7 +176,7 @@ public class TopNBenchmark
       basicQueries.put("A", queryBuilderA);
     }
     { // basic.numericSort
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory("sumLongSequential", "sumLongSequential"));
@@ -192,7 +192,7 @@ public class TopNBenchmark
       basicQueries.put("numericSort", queryBuilderA);
     }
     { // basic.alphanumericSort
-      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Arrays.asList(basicSchema.getDataInterval()));
+      QuerySegmentSpec intervalSpec = new MultipleIntervalSegmentSpec(Collections.singletonList(basicSchema.getDataInterval()));
 
       List<AggregatorFactory> queryAggs = new ArrayList<>();
       queryAggs.add(new LongSumAggregatorFactory("sumLongSequential", "sumLongSequential"));

bytebuffer-collections/src/main/java/io/druid/collections/bitmap/WrappedConciseBitmap.java

@@ -42,7 +42,7 @@ public class WrappedConciseBitmap implements MutableBitmap
   }
 
   /**
-   * Create a bitmap wrappign the given bitmap
+   * Create a bitmap wrapping the given bitmap
    *
    * @param conciseSet bitmap to be wrapped
    */

common/src/test/java/io/druid/collections/OrderedMergeSequenceTest.java

@@ -37,6 +37,7 @@ import org.junit.Test;
 import javax.annotation.Nullable;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 
@@ -367,7 +368,7 @@ public class OrderedMergeSequenceTest
         )
     );
 
-    SequenceTestHelper.testAll(finalMerged, Arrays.asList(1));
+    SequenceTestHelper.testAll(finalMerged, Collections.singletonList(1));
   }
 
   @Test
@@ -379,6 +380,6 @@ public class OrderedMergeSequenceTest
         )
     );
 
-    SequenceTestHelper.testAll(seq1, Arrays.asList(1));
+    SequenceTestHelper.testAll(seq1, Collections.singletonList(1));
   }
 }

common/src/test/java/io/druid/common/guava/CombiningSequenceTest.java

@@ -40,6 +40,7 @@ import java.io.Closeable;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
@@ -92,11 +93,11 @@ public class CombiningSequenceTest
   @Test
   public void testNoMergeOne() throws Exception
   {
-    List<Pair<Integer, Integer>> pairs = Arrays.asList(
+    List<Pair<Integer, Integer>> pairs = Collections.singletonList(
         Pair.of(0, 1)
     );
 
-    List<Pair<Integer, Integer>> expected = Arrays.asList(
+    List<Pair<Integer, Integer>> expected = Collections.singletonList(
         Pair.of(0, 1)
     );
 
@@ -151,7 +152,7 @@ public class CombiningSequenceTest
         Pair.of(0, 1)
     );
 
-    List<Pair<Integer, Integer>> expected = Arrays.asList(
+    List<Pair<Integer, Integer>> expected = Collections.singletonList(
         Pair.of(0, 2)
     );
 

common/src/test/java/io/druid/common/utils/JodaUtilsTest.java

@@ -56,7 +56,7 @@ public class JodaUtilsTest
   @Test
   public void testUmbrellaIntervalsNull() throws Exception
   {
-    List<Interval> intervals = Arrays.asList();
+    List<Interval> intervals = Collections.emptyList();
     Throwable thrown = null;
     try {
       Interval res = JodaUtils.umbrellaInterval(intervals);

common/src/test/java/io/druid/timeline/VersionedIntervalTimelineTest.java

@@ -42,6 +42,7 @@ import org.junit.Before;
 import org.junit.Test;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
@@ -157,7 +158,7 @@ public class VersionedIntervalTimelineTest
   public void testMay() throws Exception
   {
     assertValues(
-        Arrays.asList(
+        Collections.singletonList(
             createExpected("2011-05-01/2011-05-09", "4", 9)
         ),
         timeline.lookup(new Interval("2011-05-01/2011-05-09"))
@@ -216,7 +217,7 @@ public class VersionedIntervalTimelineTest
     add(new Interval(overallStart, overallStart.plus(Days.ONE)), "2", 2);
 
     assertValues(
-        Arrays.asList(
+        Collections.singletonList(
             createExpected(oneHourInterval1.toString(), "2", 2)
         ),
         timeline.lookup(oneHourInterval1)
@@ -380,7 +381,7 @@ public class VersionedIntervalTimelineTest
   {
     add("2011-05-01/2011-05-10", "5", 10);
     assertValues(
-        Arrays.asList(
+        Collections.singletonList(
             createExpected("2011-05-01/2011-05-09", "5", 10)
         ),
         timeline.lookup(new Interval("2011-05-01/2011-05-09"))
@@ -391,7 +392,7 @@ public class VersionedIntervalTimelineTest
         timeline.remove(new Interval("2011-05-01/2011-05-10"), "5", makeSingle(10))
     );
     assertValues(
-        Arrays.asList(
+        Collections.singletonList(
             createExpected("2011-05-01/2011-05-09", "4", 9)
         ),
         timeline.lookup(new Interval("2011-05-01/2011-05-09"))
@@ -399,7 +400,7 @@ public class VersionedIntervalTimelineTest
 
     add("2011-05-01/2011-05-10", "5", 10);
     assertValues(
-        Arrays.asList(
+        Collections.singletonList(
             createExpected("2011-05-01/2011-05-09", "5", 10)
         ),
         timeline.lookup(new Interval("2011-05-01/2011-05-09"))
@@ -410,7 +411,7 @@ public class VersionedIntervalTimelineTest
         timeline.remove(new Interval("2011-05-01/2011-05-10"), "4", makeSingle(9))
     );
     assertValues(
-        Arrays.asList(
+        Collections.singletonList(
             createExpected("2011-05-01/2011-05-09", "5", 10)
         ),
         timeline.lookup(new Interval("2011-05-01/2011-05-09"))
@@ -450,7 +451,7 @@ public class VersionedIntervalTimelineTest
     add("2011-01-01/2011-01-10", "1", 4);
 
     assertValues(
-        Arrays.asList(
+        Collections.singletonList(
             createExpected("2011-01-01/2011-01-10", "2", 2)
         ),
         timeline.lookup(new Interval("2011-01-01/2011-01-10"))
@@ -1177,7 +1178,7 @@ public class VersionedIntervalTimelineTest
     timeline.remove(new Interval("2011-01-10/2011-01-15"), "2", makeSingle(2));
 
     assertValues(
-        Arrays.asList(
+        Collections.singletonList(
             createExpected("2011-01-01/2011-01-20", "1", 1)
         ),
         timeline.lookup(new Interval("2011-01-01/2011-01-20"))
@@ -1218,7 +1219,7 @@ public class VersionedIntervalTimelineTest
     timeline.remove(new Interval("2011-01-10/2011-01-14"), "2", makeSingle(3));
 
     assertValues(
-        Arrays.asList(
+        Collections.singletonList(
             createExpected("2011-01-01/2011-01-20", "1", 1)
 
         ),
@@ -1258,7 +1259,7 @@ public class VersionedIntervalTimelineTest
     add("2011-01-01/2011-01-20", "1", 1);
 
     assertValues(
-        Arrays.asList(
+        Collections.singletonList(
             createExpected("2011-01-01/2011-01-20", "1", 1)
         ),
         timeline.lookup(new Interval("2011-01-01/2011-01-20"))

extensions-contrib/distinctcount/src/main/java/io/druid/query/aggregation/distinctcount/DistinctCountAggregatorFactory.java

@@ -37,6 +37,7 @@ import io.druid.segment.DimensionSelector;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
@@ -168,7 +169,7 @@ public class DistinctCountAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return Arrays.asList(fieldName);
+    return Collections.singletonList(fieldName);
   }
 
   @Override

extensions-contrib/distinctcount/src/test/java/io/druid/query/aggregation/distinctcount/DistinctCountTimeseriesQueryTest.java

@@ -21,7 +21,6 @@ package io.druid.query.aggregation.distinctcount;
 
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
-
 import io.druid.data.input.MapBasedInputRow;
 import io.druid.java.util.common.granularity.Granularities;
 import io.druid.java.util.common.guava.Sequences;
@@ -40,7 +39,7 @@ import io.druid.segment.incremental.OnheapIncrementalIndex;
 import org.joda.time.DateTime;
 import org.junit.Test;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 public class DistinctCountTimeseriesQueryTest
@@ -100,7 +99,7 @@ public class DistinctCountTimeseriesQueryTest
         Lists.<Result<TimeseriesResultValue>>newLinkedList()
     );
 
-    List<Result<TimeseriesResultValue>> expectedResults = Arrays.asList(
+    List<Result<TimeseriesResultValue>> expectedResults = Collections.singletonList(
         new Result<>(
             time,
             new TimeseriesResultValue(

extensions-contrib/distinctcount/src/test/java/io/druid/query/aggregation/distinctcount/DistinctCountTopNQueryTest.java

@@ -44,6 +44,7 @@ import org.junit.Test;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -118,7 +119,7 @@ public class DistinctCountTopNQueryTest
         Lists.<Result<TopNResultValue>>newLinkedList()
     );
 
-    List<Result<TopNResultValue>> expectedResults = Arrays.asList(
+    List<Result<TopNResultValue>> expectedResults = Collections.singletonList(
         new Result<>(
             time,
             new TopNResultValue(

extensions-contrib/orc-extensions/src/main/java/io/druid/data/input/orc/OrcExtensionsModule.java

@@ -24,14 +24,14 @@ import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.google.inject.Binder;
 import io.druid.initialization.DruidModule;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 public class OrcExtensionsModule implements DruidModule
 {
   @Override
   public List<? extends Module> getJacksonModules() {
-    return Arrays.asList(
+    return Collections.singletonList(
         new SimpleModule("OrcInputRowParserModule")
             .registerSubtypes(
                 new NamedType(OrcHadoopInputRowParser.class, "orc")

extensions-contrib/parquet-extensions/src/main/java/io/druid/data/input/parquet/ParquetExtensionsModule.java

@@ -25,7 +25,7 @@ import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.google.inject.Binder;
 import io.druid.initialization.DruidModule;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 public class ParquetExtensionsModule implements DruidModule
@@ -34,8 +34,8 @@ public class ParquetExtensionsModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Arrays.asList(
+    return Collections.singletonList(
-        new SimpleModule("ParuqetInputRowParserModule")
+        new SimpleModule("ParquetInputRowParserModule")
             .registerSubtypes(
                 new NamedType(ParquetHadoopInputRowParser.class, "parquet")
             )

extensions-contrib/scan-query/src/test/java/io/druid/query/scan/ScanQueryRunnerTest.java

@@ -47,6 +47,7 @@ import org.junit.runners.Parameterized;
 
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
@@ -414,8 +415,7 @@ public class ScanQueryRunnerTest
         Lists.<ScanResultValue>newArrayList()
     );
 
-    List<ScanResultValue> expectedResults = Arrays.asList(
+    List<ScanResultValue> expectedResults = Collections.emptyList();
-    );
 
     verify(expectedResults, populateNullColumnAtLastForQueryableIndexCase(results, "null_column"));
   }

extensions-contrib/thrift-extensions/src/main/java/io/druid/data/input/thrift/ThriftExtensionsModule.java

@@ -25,7 +25,7 @@ import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.google.inject.Binder;
 import io.druid.initialization.DruidModule;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 public class ThriftExtensionsModule implements DruidModule
@@ -34,7 +34,7 @@ public class ThriftExtensionsModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Arrays.asList(
+    return Collections.singletonList(
         new SimpleModule("ThriftInputRowParserModule")
             .registerSubtypes(
                 new NamedType(ThriftInputRowParser.class, "thrift")

extensions-contrib/time-min-max/src/main/java/io/druid/query/aggregation/TimestampAggregatorFactory.java

@@ -29,6 +29,7 @@ import org.joda.time.DateTime;
 import java.nio.ByteBuffer;
 import java.sql.Timestamp;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
@@ -142,7 +143,7 @@ public class TimestampAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return Arrays.asList(fieldName);
+    return Collections.singletonList(fieldName);
   }
 
   @Override

extensions-contrib/time-min-max/src/main/java/io/druid/query/aggregation/TimestampMinMaxModule.java

@@ -24,7 +24,7 @@ import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.google.inject.Binder;
 import io.druid.initialization.DruidModule;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 public class TimestampMinMaxModule implements DruidModule
@@ -32,7 +32,7 @@ public class TimestampMinMaxModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Arrays.asList(
+    return Collections.singletonList(
         new SimpleModule("TimestampMinMaxModule")
             .registerSubtypes(
                 new NamedType(TimestampMaxAggregatorFactory.class, "timeMax"),

extensions-contrib/virtual-columns/src/test/java/io/druid/segment/MapVirtualColumnTest.java

@@ -55,6 +55,7 @@ import org.junit.runners.Parameterized;
 
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -164,8 +165,8 @@ public class MapVirtualColumnTest
             "params", mapOf("key1", "value1", "key5", "value5")
         )
     );
-    List<VirtualColumn> virtualColumns = Arrays.<VirtualColumn>asList(new MapVirtualColumn("keys", "values", "params"));
+    List<VirtualColumn> virtualColumns = Collections.singletonList(new MapVirtualColumn("keys", "values", "params"));
-    SelectQuery selectQuery = builder.dimensions(Arrays.asList("dim"))
+    SelectQuery selectQuery = builder.dimensions(Collections.singletonList("dim"))
                                      .metrics(Arrays.asList("params.key1", "params.key3", "params.key5", "params"))
                                      .virtualColumns(virtualColumns)
                                      .build();

extensions-core/avro-extensions/src/main/java/io/druid/data/input/avro/SchemaRepoBasedAvroBytesDecoder.java

@@ -80,14 +80,12 @@ public class SchemaRepoBasedAvroBytesDecoder<SUBJECT, ID> implements AvroBytesDe
     DatumReader<GenericRecord> reader = new GenericDatumReader<>(schema);
     try (ByteBufferInputStream inputStream = new ByteBufferInputStream(Collections.singletonList(bytes))) {
       return reader.read(null, DecoderFactory.get().binaryDecoder(inputStream, null));
-    }
+    } catch (EOFException eof) {
-    catch (EOFException eof) {
       // waiting for avro v1.9.0 (#AVRO-813)
       throw new ParseException(
           eof, "Avro's unnecessary EOFException, detail: [%s]", "https://issues.apache.org/jira/browse/AVRO-813"
       );
-    }
+    } catch (IOException e) {
-    catch (IOException e) {
       throw new ParseException(e, "Fail to decode avro message!");
     }
   }

extensions-core/hdfs-storage/src/test/java/io/druid/segment/loading/HdfsDataSegmentPullerTest.java

@@ -20,7 +20,6 @@
 package io.druid.segment.loading;
 
 import com.google.common.io.ByteStreams;
-
 import io.druid.java.util.common.CompressionUtils;
 import io.druid.java.util.common.StringUtils;
 import io.druid.storage.hdfs.HdfsDataSegmentPuller;
@@ -165,13 +164,11 @@ public class HdfsDataSegmentPullerTest
 
     final URI uri = URI.create(uriBase.toString() + zipPath.toString());
 
-    try (final OutputStream outputStream = miniCluster.getFileSystem().create(zipPath)) {
+    try (final OutputStream outputStream = miniCluster.getFileSystem().create(zipPath);
-      try (final OutputStream gzStream = new GZIPOutputStream(outputStream)) {
+         final OutputStream gzStream = new GZIPOutputStream(outputStream);
-        try (final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
+         final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
       ByteStreams.copy(inputStream, gzStream);
     }
-      }
-    }
     try {
       Assert.assertFalse(outFile.exists());
       puller.getSegmentFiles(uri, outTmpDir);
@@ -201,11 +198,10 @@ public class HdfsDataSegmentPullerTest
 
     final URI uri = URI.create(uriBase.toString() + perTestPath.toString());
 
-    try (final OutputStream outputStream = miniCluster.getFileSystem().create(zipPath)) {
+    try (final OutputStream outputStream = miniCluster.getFileSystem().create(zipPath);
-      try (final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
+         final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
       ByteStreams.copy(inputStream, outputStream);
     }
-    }
     try {
       Assert.assertFalse(outFile.exists());
       puller.getSegmentFiles(uri, outTmpDir);

extensions-core/hdfs-storage/src/test/java/io/druid/segment/loading/HdfsFileTimestampVersionFinderTest.java

@@ -20,7 +20,6 @@
 package io.druid.segment.loading;
 
 import com.google.common.io.ByteStreams;
-
 import io.druid.java.util.common.StringUtils;
 import io.druid.storage.hdfs.HdfsFileTimestampVersionFinder;
 import org.apache.commons.io.FileUtils;
@@ -110,21 +109,19 @@ public class HdfsFileTimestampVersionFinderTest
   {
     final Path oldPath = new Path(perTestPath, "555test.txt");
     Assert.assertFalse(miniCluster.getFileSystem().exists(oldPath));
-    try (final OutputStream outputStream = miniCluster.getFileSystem().create(oldPath)) {
+    try (final OutputStream outputStream = miniCluster.getFileSystem().create(oldPath);
-      try (final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
+         final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
       ByteStreams.copy(inputStream, outputStream);
     }
-    }
 
     Thread.sleep(10);
 
     final Path newPath = new Path(perTestPath, "666test.txt");
     Assert.assertFalse(miniCluster.getFileSystem().exists(newPath));
-    try (final OutputStream outputStream = miniCluster.getFileSystem().create(newPath)) {
+    try (final OutputStream outputStream = miniCluster.getFileSystem().create(newPath);
-      try (final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
+         final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
       ByteStreams.copy(inputStream, outputStream);
     }
-    }
 
     Assert.assertEquals(newPath.toString(), finder.getLatestVersion(oldPath.toUri(), Pattern.compile(".*")).getPath());
   }
@@ -134,21 +131,19 @@ public class HdfsFileTimestampVersionFinderTest
   {
     final Path oldPath = new Path(perTestPath, "555test.txt");
     Assert.assertFalse(miniCluster.getFileSystem().exists(oldPath));
-    try (final OutputStream outputStream = miniCluster.getFileSystem().create(oldPath)) {
+    try (final OutputStream outputStream = miniCluster.getFileSystem().create(oldPath);
-      try (final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
+         final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
       ByteStreams.copy(inputStream, outputStream);
     }
-    }
 
     Thread.sleep(10);
 
     final Path newPath = new Path(perTestPath, "666test.txt");
     Assert.assertFalse(miniCluster.getFileSystem().exists(newPath));
-    try (final OutputStream outputStream = miniCluster.getFileSystem().create(newPath)) {
+    try (final OutputStream outputStream = miniCluster.getFileSystem().create(newPath);
-      try (final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
+         final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
       ByteStreams.copy(inputStream, outputStream);
     }
-    }
 
     Assert.assertEquals(newPath.toString(), finder.getLatestVersion(newPath.toUri(), Pattern.compile(".*")).getPath());
   }
@@ -166,21 +161,19 @@ public class HdfsFileTimestampVersionFinderTest
   {
     final Path oldPath = new Path(perTestPath, "555test.txt");
     Assert.assertFalse(miniCluster.getFileSystem().exists(oldPath));
-    try (final OutputStream outputStream = miniCluster.getFileSystem().create(oldPath)) {
+    try (final OutputStream outputStream = miniCluster.getFileSystem().create(oldPath);
-      try (final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
+         final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
       ByteStreams.copy(inputStream, outputStream);
     }
-    }
 
     Thread.sleep(10);
 
     final Path newPath = new Path(perTestPath, "666test.txt");
     Assert.assertFalse(miniCluster.getFileSystem().exists(newPath));
-    try (final OutputStream outputStream = miniCluster.getFileSystem().create(newPath)) {
+    try (final OutputStream outputStream = miniCluster.getFileSystem().create(newPath);
-      try (final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
+         final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
       ByteStreams.copy(inputStream, outputStream);
     }
-    }
 
     Assert.assertEquals(
         newPath.toString(),
@@ -193,21 +186,19 @@ public class HdfsFileTimestampVersionFinderTest
   {
     final Path oldPath = new Path(perTestPath, "555test.txt");
     Assert.assertFalse(miniCluster.getFileSystem().exists(oldPath));
-    try (final OutputStream outputStream = miniCluster.getFileSystem().create(oldPath)) {
+    try (final OutputStream outputStream = miniCluster.getFileSystem().create(oldPath);
-      try (final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
+         final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
       ByteStreams.copy(inputStream, outputStream);
     }
-    }
 
     Thread.sleep(10);
 
     final Path newPath = new Path(perTestPath, "666test.txt2");
     Assert.assertFalse(miniCluster.getFileSystem().exists(newPath));
-    try (final OutputStream outputStream = miniCluster.getFileSystem().create(newPath)) {
+    try (final OutputStream outputStream = miniCluster.getFileSystem().create(newPath);
-      try (final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
+         final InputStream inputStream = new ByteArrayInputStream(pathByteContents)) {
       ByteStreams.copy(inputStream, outputStream);
     }
-    }
 
     Assert.assertEquals(
         oldPath.toString(),

extensions-core/histogram/src/main/java/io/druid/query/aggregation/histogram/ApproximateHistogramAggregatorFactory.java

@@ -37,6 +37,7 @@ import org.apache.commons.codec.binary.Base64;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
@@ -225,7 +226,7 @@ public class ApproximateHistogramAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return Arrays.asList(fieldName);
+    return Collections.singletonList(fieldName);
   }
 
   @Override

extensions-core/histogram/src/test/java/io/druid/query/aggregation/histogram/ApproximateHistogramGroupByQueryTest.java

@@ -24,7 +24,6 @@ import com.google.common.collect.Lists;
 import io.druid.data.input.Row;
 import io.druid.query.QueryRunner;
 import io.druid.query.QueryRunnerTestHelper;
-import io.druid.query.aggregation.PostAggregator;
 import io.druid.query.dimension.DefaultDimensionSpec;
 import io.druid.query.dimension.DimensionSpec;
 import io.druid.query.groupby.GroupByQuery;
@@ -42,6 +41,7 @@ import org.junit.runners.Parameterized;
 
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -181,13 +181,13 @@ public class ApproximateHistogramGroupByQueryTest
             )
         )
         .setPostAggregatorSpecs(
-            Arrays.<PostAggregator>asList(
+            Collections.singletonList(
                 new QuantilePostAggregator("quantile", "apphisto", 0.5f)
             )
         )
         .build();
 
-    List<Row> expectedResults = Arrays.asList(
+    List<Row> expectedResults = Collections.singletonList(
         GroupByQueryRunnerTestHelper.createExpectedRow(
             "1970-01-01T00:00:00.000Z",
             "marketalias", "upfront",
@@ -255,13 +255,13 @@ public class ApproximateHistogramGroupByQueryTest
             )
         )
         .setPostAggregatorSpecs(
-            Arrays.<PostAggregator>asList(
+            Collections.singletonList(
                 new QuantilePostAggregator("quantile", "quantile", 0.5f)
             )
         )
         .build();
 
-    List<Row> expectedResults = Arrays.asList(
+    List<Row> expectedResults = Collections.singletonList(
         GroupByQueryRunnerTestHelper.createExpectedRow(
             "1970-01-01T00:00:00.000Z",
             "marketalias", "upfront",

extensions-core/histogram/src/test/java/io/druid/query/aggregation/histogram/ApproximateHistogramTopNQueryTest.java

@@ -47,6 +47,7 @@ import org.junit.runners.Parameterized;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -62,7 +63,10 @@ public class ApproximateHistogramTopNQueryTest
             QueryRunnerTestHelper.makeQueryRunners(
                 new TopNQueryRunnerFactory(
                     TestQueryRunners.getPool(),
-                    new TopNQueryQueryToolChest(new TopNQueryConfig(), QueryRunnerTestHelper.NoopIntervalChunkingQueryRunnerDecorator()),
+                    new TopNQueryQueryToolChest(
+                        new TopNQueryConfig(),
+                        QueryRunnerTestHelper.NoopIntervalChunkingQueryRunnerDecorator()
+                    ),
                     QueryRunnerTestHelper.NOOP_QUERYWATCHER
                 )
             ),
@@ -79,7 +83,10 @@ public class ApproximateHistogramTopNQueryTest
                           }
                         }
                     ),
-                    new TopNQueryQueryToolChest(new TopNQueryConfig(), QueryRunnerTestHelper.NoopIntervalChunkingQueryRunnerDecorator()),
+                    new TopNQueryQueryToolChest(
+                        new TopNQueryConfig(),
+                        QueryRunnerTestHelper.NoopIntervalChunkingQueryRunnerDecorator()
+                    ),
                     QueryRunnerTestHelper.NOOP_QUERYWATCHER
                 )
             )
@@ -136,7 +143,7 @@ public class ApproximateHistogramTopNQueryTest
         )
         .build();
 
-    List<Result<TopNResultValue>> expectedResults = Arrays.asList(
+    List<Result<TopNResultValue>> expectedResults = Collections.singletonList(
         new Result<TopNResultValue>(
             new DateTime("2011-01-12T00:00:00.000Z"),
             new TopNResultValue(

extensions-core/lookups-cached-global/src/test/java/io/druid/server/lookup/namespace/URIExtractionNamespaceCacheFactoryTest.java

@@ -275,8 +275,8 @@ public class URIExtractionNamespaceCacheFactoryTest
     Assert.assertTrue(tmpFileParent.isDirectory());
     tmpFile = Files.createTempFile(tmpFileParent.toPath(), "druidTestURIExtractionNS", suffix).toFile();
     final ObjectMapper mapper = new DefaultObjectMapper();
-    try (OutputStream ostream = outStreamSupplier.apply(tmpFile)) {
+    try (OutputStream ostream = outStreamSupplier.apply(tmpFile);
-      try (OutputStreamWriter out = new OutputStreamWriter(ostream)) {
+         OutputStreamWriter out = new OutputStreamWriter(ostream)) {
       out.write(mapper.writeValueAsString(ImmutableMap.<String, String>of(
           "boo",
           "bar",
@@ -288,7 +288,6 @@ public class URIExtractionNamespaceCacheFactoryTest
           ""
       )));
     }
-    }
     populator = new URIExtractionNamespaceCacheFactory(FINDERS);
     namespace = new URIExtractionNamespace(
         tmpFile.toURI(),

extensions-core/stats/src/main/java/io/druid/query/aggregation/variance/VarianceAggregatorFactory.java

@@ -37,6 +37,7 @@ import org.apache.commons.codec.binary.Base64;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
@@ -218,7 +219,7 @@ public class VarianceAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return Arrays.asList(fieldName);
+    return Collections.singletonList(fieldName);
   }
 
   @Override

indexing-hadoop/src/main/java/io/druid/indexer/IndexGeneratorJob.java

@@ -775,10 +775,7 @@ public class IndexGeneratorJob implements Jobby
           FileUtils.deleteDirectory(file);
         }
       }
-      catch (ExecutionException e) {
+      catch (ExecutionException | TimeoutException e) {
-        throw Throwables.propagate(e);
-      }
-      catch (TimeoutException e) {
         throw Throwables.propagate(e);
       }
       finally {

indexing-hadoop/src/test/java/io/druid/indexer/IndexGeneratorCombinerTest.java

@@ -46,6 +46,7 @@ import org.junit.Before;
 import org.junit.Test;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -245,14 +246,14 @@ public class IndexGeneratorCombinerTest
 
     InputRow capturedRow1 = InputRowSerde.fromBytes(captureVal1.getValue().getBytes(), aggregators);
     Assert.assertEquals(Arrays.asList("host", "keywords"), capturedRow1.getDimensions());
-    Assert.assertEquals(Arrays.asList("host1"), capturedRow1.getDimension("host"));
+    Assert.assertEquals(Collections.singletonList("host1"), capturedRow1.getDimension("host"));
     Assert.assertEquals(Arrays.asList("bar", "foo"), capturedRow1.getDimension("keywords"));
     Assert.assertEquals(10, capturedRow1.getLongMetric("visited_sum"));
     Assert.assertEquals(1.0, (Double)HyperUniquesAggregatorFactory.estimateCardinality(capturedRow1.getRaw("unique_hosts")), 0.001);
 
     InputRow capturedRow2 = InputRowSerde.fromBytes(captureVal2.getValue().getBytes(), aggregators);
     Assert.assertEquals(Arrays.asList("host", "keywords"), capturedRow2.getDimensions());
-    Assert.assertEquals(Arrays.asList("host2"), capturedRow2.getDimension("host"));
+    Assert.assertEquals(Collections.singletonList("host2"), capturedRow2.getDimension("host"));
     Assert.assertEquals(Arrays.asList("bar", "foo"), capturedRow2.getDimension("keywords"));
     Assert.assertEquals(5, capturedRow2.getLongMetric("visited_sum"));
     Assert.assertEquals(1.0, (Double)HyperUniquesAggregatorFactory.estimateCardinality(capturedRow2.getRaw("unique_hosts")), 0.001);

indexing-hadoop/src/test/java/io/druid/indexer/UtilsCompressionTest.java

@@ -86,7 +86,8 @@ public class UtilsCompressionTest
     tmpFolder.delete();
   }
 
-  @Test public void testExistsCompressedFile() throws IOException
+  @Test
+  public void testExistsCompressedFile() throws IOException
   {
     boolean expected = Utils.exists(mockJobContext, defaultFileSystem, tmpPathWithoutExtension);
     Assert.assertTrue("Should be true since file is created", expected);

indexing-hadoop/src/test/java/io/druid/indexer/UtilsTest.java

@@ -22,9 +22,7 @@ package io.druid.indexer;
 import com.google.common.base.Function;
 import com.google.common.collect.Maps;
 import com.google.common.io.ByteStreams;
-
 import io.druid.java.util.common.ISE;
-
 import org.apache.commons.io.FileUtils;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileSystem;
@@ -67,7 +65,8 @@ public class UtilsTest
 
   private static class CreateValueFromKey implements Function
   {
-    @Override public Object apply(Object input)
+    @Override
+    public Object apply(Object input)
     {
       return input.toString() + DUMMY_STRING;
     }

indexing-service/src/main/java/io/druid/indexing/common/SegmentLoaderFactory.java

@@ -26,7 +26,7 @@ import io.druid.segment.loading.SegmentLoaderLocalCacheManager;
 import io.druid.segment.loading.StorageLocationConfig;
 
 import java.io.File;
-import java.util.Arrays;
+import java.util.Collections;
 
 /**
  */
@@ -45,7 +45,7 @@ public class SegmentLoaderFactory
   public SegmentLoader manufacturate(File storageDir)
   {
     return loader.withConfig(
-        new SegmentLoaderConfig().withLocations(Arrays.asList(new StorageLocationConfig().setPath(storageDir)))
+        new SegmentLoaderConfig().withLocations(Collections.singletonList(new StorageLocationConfig().setPath(storageDir)))
     );
   }
 }

indexing-service/src/test/java/io/druid/indexing/common/actions/RemoteTaskActionClientTest.java

@@ -19,11 +19,13 @@
 
 package io.druid.indexing.common.actions;
 
-import static org.easymock.EasyMock.anyObject;
+import com.fasterxml.jackson.core.JsonProcessingException;
-import static org.easymock.EasyMock.createMock;
+import com.fasterxml.jackson.databind.ObjectMapper;
-import static org.easymock.EasyMock.expect;
+import com.google.common.util.concurrent.Futures;
-import static org.easymock.EasyMock.replay;
+import com.metamx.http.client.HttpClient;
-
+import com.metamx.http.client.Request;
+import com.metamx.http.client.response.StatusResponseHandler;
+import com.metamx.http.client.response.StatusResponseHolder;
 import io.druid.client.selector.Server;
 import io.druid.curator.discovery.ServerDiscoverySelector;
 import io.druid.indexing.common.RetryPolicyConfig;
@@ -32,13 +34,6 @@ import io.druid.indexing.common.TaskLock;
 import io.druid.indexing.common.task.NoopTask;
 import io.druid.indexing.common.task.Task;
 import io.druid.jackson.DefaultObjectMapper;
-
-import java.io.IOException;
-import java.util.Arrays;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
 import org.easymock.EasyMock;
 import org.jboss.netty.handler.codec.http.HttpResponseStatus;
 import org.joda.time.Interval;
@@ -46,13 +41,16 @@ import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
-import com.fasterxml.jackson.core.JsonProcessingException;
+import java.io.IOException;
-import com.fasterxml.jackson.databind.ObjectMapper;
+import java.util.Collections;
-import com.google.common.util.concurrent.Futures;
+import java.util.HashMap;
-import com.metamx.http.client.HttpClient;
+import java.util.List;
-import com.metamx.http.client.Request;
+import java.util.Map;
-import com.metamx.http.client.response.StatusResponseHandler;
+
-import com.metamx.http.client.response.StatusResponseHolder;
+import static org.easymock.EasyMock.anyObject;
+import static org.easymock.EasyMock.createMock;
+import static org.easymock.EasyMock.expect;
+import static org.easymock.EasyMock.replay;
 
 public class RemoteTaskActionClientTest
 {
@@ -99,7 +97,12 @@ public class RemoteTaskActionClientTest
 
     long now = System.currentTimeMillis();
 
-    result = Arrays.asList(new TaskLock("groupId", "dataSource", new Interval(now - 30 * 1000, now), "version"));
+    result = Collections.singletonList(new TaskLock(
+        "groupId",
+        "dataSource",
+        new Interval(now - 30 * 1000, now),
+        "version"
+    ));
   }
 
   @Test

indexing-service/src/test/java/io/druid/indexing/common/task/IndexTaskTest.java

@@ -207,7 +207,7 @@ public class IndexTaskTest
             null,
             new ArbitraryGranularitySpec(
                 Granularities.MINUTE,
-                Arrays.asList(new Interval("2014/2015"))
+                Collections.singletonList(new Interval("2014/2015"))
             ),
             10,
             null,
@@ -244,7 +244,7 @@ public class IndexTaskTest
             new UniformGranularitySpec(
                 Granularities.HOUR,
                 Granularities.HOUR,
-                Arrays.asList(new Interval("2015-03-01T08:00:00Z/2015-03-01T09:00:00Z"))
+                Collections.singletonList(new Interval("2015-03-01T08:00:00Z/2015-03-01T09:00:00Z"))
             ),
             50,
             null,
@@ -497,7 +497,7 @@ public class IndexTaskTest
           public <RetType> RetType submit(TaskAction<RetType> taskAction) throws IOException
           {
             if (taskAction instanceof LockListAction) {
-              return (RetType) Arrays.asList(
+              return (RetType) Collections.singletonList(
                   new TaskLock(
                       "", "", null, new DateTime().toString()
                   )

indexing-service/src/test/java/io/druid/indexing/overlord/autoscaling/EC2AutoScalerTest.java

@@ -128,7 +128,7 @@ public class EC2AutoScalerTest
     Assert.assertEquals(created.getNodeIds().size(), 1);
     Assert.assertEquals("theInstance", created.getNodeIds().get(0));
 
-    AutoScalingData deleted = autoScaler.terminate(Arrays.asList("dummyIP"));
+    AutoScalingData deleted = autoScaler.terminate(Collections.singletonList("dummyIP"));
 
     Assert.assertEquals(deleted.getNodeIds().size(), 1);
     Assert.assertEquals(INSTANCE_ID, deleted.getNodeIds().get(0));
@@ -185,7 +185,7 @@ public class EC2AutoScalerTest
     );
     EasyMock.replay(describeInstancesResult);
 
-    EasyMock.expect(reservation.getInstances()).andReturn(Arrays.asList(instance)).times(n);
+    EasyMock.expect(reservation.getInstances()).andReturn(Collections.singletonList(instance)).times(n);
     EasyMock.replay(reservation);
 
     List<String> ids = autoScaler.ipToIdLookup(ips);

java-util/src/main/java/io/druid/java/util/common/io/smoosh/FileSmoosher.java

@@ -46,7 +46,7 @@ import java.nio.ByteBuffer;
 import java.nio.channels.Channels;
 import java.nio.channels.GatheringByteChannel;
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -134,7 +134,7 @@ public class FileSmoosher implements Closeable
 
   public void add(String name, ByteBuffer bufferToAdd) throws IOException
   {
-    add(name, Arrays.asList(bufferToAdd));
+    add(name, Collections.singletonList(bufferToAdd));
   }
 
   public void add(String name, List<ByteBuffer> bufferToAdd) throws IOException

processing/src/main/java/io/druid/query/BySegmentQueryRunner.java

@@ -24,7 +24,7 @@ import io.druid.java.util.common.guava.Sequence;
 import io.druid.java.util.common.guava.Sequences;
 import org.joda.time.DateTime;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -55,7 +55,7 @@ public class BySegmentQueryRunner<T> implements QueryRunner<T>
       final Sequence<T> baseSequence = base.run(queryPlus, responseContext);
       final List<T> results = Sequences.toList(baseSequence, Lists.<T>newArrayList());
       return Sequences.simple(
-          Arrays.asList(
+          Collections.singletonList(
               (T) new Result<BySegmentResultValueClass<T>>(
                   timestamp,
                   new BySegmentResultValueClass<T>(

processing/src/main/java/io/druid/query/ChainedExecutionQueryRunner.java

@@ -133,11 +133,9 @@ public class ChainedExecutionQueryRunner<T> implements QueryRunner<T>
                                       }
 
                                       return retVal;
-                                    }
+                                    } catch (QueryInterruptedException e) {
-                                    catch (QueryInterruptedException e) {
                                       throw Throwables.propagate(e);
-                                    }
+                                    } catch (Exception e) {
-                                    catch (Exception e) {
                                       log.error(e, "Exception with one of the sequences!");
                                       throw Throwables.propagate(e);
                                     }
@@ -159,21 +157,17 @@ public class ChainedExecutionQueryRunner<T> implements QueryRunner<T>
                       futures.get(QueryContexts.getTimeout(query), TimeUnit.MILLISECONDS) :
                       futures.get()
               ).iterator();
-            }
+            } catch (InterruptedException e) {
-            catch (InterruptedException e) {
               log.warn(e, "Query interrupted, cancelling pending results, query id [%s]", query.getId());
               futures.cancel(true);
               throw new QueryInterruptedException(e);
-            }
+            } catch (CancellationException e) {
-            catch (CancellationException e) {
               throw new QueryInterruptedException(e);
-            }
+            } catch (TimeoutException e) {
-            catch (TimeoutException e) {
               log.info("Query timeout, cancelling pending results for query id [%s]", query.getId());
               futures.cancel(true);
               throw new QueryInterruptedException(e);
-            }
+            } catch (ExecutionException e) {
-            catch (ExecutionException e) {
               throw Throwables.propagate(e.getCause());
             }
           }

processing/src/main/java/io/druid/query/IntervalChunkingQueryRunner.java

@@ -31,7 +31,7 @@ import org.joda.time.DateTime;
 import org.joda.time.Interval;
 import org.joda.time.Period;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -113,7 +113,8 @@ public class IntervalChunkingQueryRunner<T> implements QueryRunner<T>
                         ),
                         executor, queryWatcher
                     ).run(
-                        queryPlus.withQuerySegmentSpec(new MultipleIntervalSegmentSpec(Arrays.asList(singleInterval))),
+                        queryPlus.withQuerySegmentSpec(
+                            new MultipleIntervalSegmentSpec(Collections.singletonList(singleInterval))),
                         responseContext
                     );
                   }

processing/src/main/java/io/druid/query/TableDataSource.java

@@ -22,7 +22,7 @@ import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonTypeName;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 @JsonTypeName("table")
@@ -45,7 +45,7 @@ public class TableDataSource implements DataSource
   @Override
   public List<String> getNames()
   {
-    return Arrays.asList(name);
+    return Collections.singletonList(name);
   }
 
   public String toString() { return name; }

processing/src/main/java/io/druid/query/TimewarpOperator.java

@@ -35,12 +35,10 @@ import org.joda.time.Period;
 import java.util.Arrays;
 import java.util.Map;
 
-
 /**
  * TimewarpOperator is an example post-processing operator that maps current time
  * to the latest period ending withing the specified data interval and truncates
  * the query interval to discard data that would be mapped to the future.
- *
  */
 public class TimewarpOperator<T> implements PostProcessingOperator<T>
 {
@@ -49,7 +47,6 @@ public class TimewarpOperator<T> implements PostProcessingOperator<T>
   private final long originMillis;
 
   /**
-   *
    * @param dataInterval interval containing the actual data
    * @param period       time will be offset by a multiple of the given period
    *                     until there is at least a full period ending within the data interval
@@ -69,7 +66,6 @@ public class TimewarpOperator<T> implements PostProcessingOperator<T>
     this.periodMillis = period.toStandardDuration().getMillis();
   }
 
-
   @Override
   public QueryRunner<T> postProcess(QueryRunner<T> baseQueryRunner)
   {
@@ -109,7 +105,8 @@ public class TimewarpOperator<T> implements PostProcessingOperator<T>
                     DateTime minTime = null;
                     try {
                       minTime = boundary.getMinTime();
-                    } catch(IllegalArgumentException e) {}
+                    } catch (IllegalArgumentException e) {
+                    }
 
                     final DateTime maxTime = boundary.getMaxTime();
 
@@ -138,6 +135,7 @@ public class TimewarpOperator<T> implements PostProcessingOperator<T>
    * Map time t into the last `period` ending within `dataInterval`
    *
    * @param t the current time to be mapped into `dataInterval`
+   *
    * @return the offset between the mapped time and time t
    */
   protected long computeOffset(final long t)
@@ -147,7 +145,8 @@ public class TimewarpOperator<T> implements PostProcessingOperator<T>
     long startOffset = start % periodMillis - originMillis % periodMillis;
     if (startOffset < 0) {
       startOffset += periodMillis;
-    };
+    }
+    ;
     start -= startOffset;
 
     // tOffset is the offset time t within the last period

processing/src/main/java/io/druid/query/aggregation/DoubleMaxAggregatorFactory.java

@@ -30,6 +30,7 @@ import io.druid.segment.FloatColumnSelector;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
@@ -156,7 +157,7 @@ public class DoubleMaxAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return fieldName != null ? Arrays.asList(fieldName) : Parser.findRequiredBindings(expression);
+    return fieldName != null ? Collections.singletonList(fieldName) : Parser.findRequiredBindings(expression);
   }
 
   @Override

processing/src/main/java/io/druid/query/aggregation/DoubleMinAggregatorFactory.java

@@ -30,6 +30,7 @@ import io.druid.segment.FloatColumnSelector;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
@@ -156,7 +157,7 @@ public class DoubleMinAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return fieldName != null ? Arrays.asList(fieldName) : Parser.findRequiredBindings(expression);
+    return fieldName != null ? Collections.singletonList(fieldName) : Parser.findRequiredBindings(expression);
   }
 
   @Override

processing/src/main/java/io/druid/query/aggregation/DoubleSumAggregatorFactory.java

@@ -30,6 +30,7 @@ import io.druid.segment.FloatColumnSelector;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
@@ -156,7 +157,7 @@ public class DoubleSumAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return fieldName != null ? Arrays.asList(fieldName) : Parser.findRequiredBindings(expression);
+    return fieldName != null ? Collections.singletonList(fieldName) : Parser.findRequiredBindings(expression);
   }
 
   @Override

processing/src/main/java/io/druid/query/aggregation/LongMaxAggregatorFactory.java

@@ -30,6 +30,7 @@ import io.druid.segment.LongColumnSelector;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
@@ -152,7 +153,7 @@ public class LongMaxAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return fieldName != null ? Arrays.asList(fieldName) : Parser.findRequiredBindings(expression);
+    return fieldName != null ? Collections.singletonList(fieldName) : Parser.findRequiredBindings(expression);
   }
 
   @Override

processing/src/main/java/io/druid/query/aggregation/LongMinAggregatorFactory.java

@@ -30,6 +30,7 @@ import io.druid.segment.LongColumnSelector;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
@@ -152,7 +153,7 @@ public class LongMinAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return fieldName != null ? Arrays.asList(fieldName) : Parser.findRequiredBindings(expression);
+    return fieldName != null ? Collections.singletonList(fieldName) : Parser.findRequiredBindings(expression);
   }
 
   @Override

processing/src/main/java/io/druid/query/aggregation/LongSumAggregatorFactory.java

@@ -30,6 +30,7 @@ import io.druid.segment.LongColumnSelector;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
@@ -152,7 +153,7 @@ public class LongSumAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return fieldName != null ? Arrays.asList(fieldName) : Parser.findRequiredBindings(expression);
+    return fieldName != null ? Collections.singletonList(fieldName) : Parser.findRequiredBindings(expression);
   }
 
   @Override

processing/src/main/java/io/druid/query/aggregation/hyperloglog/HyperUniquesAggregatorFactory.java

@@ -37,6 +37,7 @@ import org.apache.commons.codec.binary.Base64;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
@@ -193,7 +194,7 @@ public class HyperUniquesAggregatorFactory extends AggregatorFactory
   @Override
   public List<String> requiredFields()
   {
-    return Arrays.asList(fieldName);
+    return Collections.singletonList(fieldName);
   }
 
   @JsonProperty

processing/src/main/java/io/druid/query/datasourcemetadata/DataSourceMetadataQuery.java

@@ -34,7 +34,6 @@ import io.druid.query.spec.QuerySegmentSpec;
 import org.joda.time.DateTime;
 import org.joda.time.Interval;
 
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
@@ -102,10 +101,12 @@ public class DataSourceMetadataQuery extends BaseQuery<Result<DataSourceMetadata
 
   public Iterable<Result<DataSourceMetadataResultValue>> buildResult(DateTime timestamp, DateTime maxIngestedEventTime)
   {
-    return Arrays.asList(new Result<>(timestamp, new DataSourceMetadataResultValue(maxIngestedEventTime)));
+    return Collections.singletonList(new Result<>(timestamp, new DataSourceMetadataResultValue(maxIngestedEventTime)));
   }
 
-  public Iterable<Result<DataSourceMetadataResultValue>> mergeResults(List<Result<DataSourceMetadataResultValue>> results)
+  public Iterable<Result<DataSourceMetadataResultValue>> mergeResults(
+      List<Result<DataSourceMetadataResultValue>> results
+  )
   {
     if (results == null || results.isEmpty()) {
       return Lists.newArrayList();

processing/src/main/java/io/druid/query/groupby/having/EqualToHavingSpec.java

@@ -26,7 +26,7 @@ import io.druid.data.input.Row;
 import io.druid.java.util.common.StringUtils;
 
 import java.nio.ByteBuffer;
-import java.util.Arrays;
+import java.util.Collections;
 
 /**
  * The "=" operator in a "having" clause. This is similar to SQL's "having aggregation = value",
@@ -71,7 +71,7 @@ public class EqualToHavingSpec extends BaseHavingSpec
   public byte[] getCacheKey()
   {
     final byte[] aggBytes = StringUtils.toUtf8(aggregationName);
-    final byte[] valBytes = Bytes.toArray(Arrays.asList(value));
+    final byte[] valBytes = Bytes.toArray(Collections.singletonList(value));
     return ByteBuffer.allocate(1 + aggBytes.length + valBytes.length)
                      .put(CACHE_KEY)
                      .put(aggBytes)

processing/src/main/java/io/druid/query/groupby/having/GreaterThanHavingSpec.java

@@ -21,12 +21,10 @@ package io.druid.query.groupby.having;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
-import com.google.common.primitives.Bytes;
 import io.druid.data.input.Row;
 import io.druid.java.util.common.StringUtils;
 
 import java.nio.ByteBuffer;
-import java.util.Arrays;
 
 /**
  * The ">" operator in a "having" clause. This is similar to SQL's "having aggregation > value",
@@ -71,7 +69,7 @@ public class GreaterThanHavingSpec extends BaseHavingSpec
   public byte[] getCacheKey()
   {
     final byte[] aggBytes = StringUtils.toUtf8(aggregationName);
-    final byte[] valBytes = Bytes.toArray(Arrays.asList(value));
+    final byte[] valBytes = new byte[] { value.byteValue() };
     return ByteBuffer.allocate(1 + aggBytes.length + valBytes.length)
         .put(CACHE_KEY)
         .put(aggBytes)

processing/src/main/java/io/druid/query/groupby/having/LessThanHavingSpec.java

@@ -25,7 +25,7 @@ import io.druid.data.input.Row;
 import io.druid.java.util.common.StringUtils;
 
 import java.nio.ByteBuffer;
-import java.util.Arrays;
+import java.util.Collections;
 
 /**
  * The "<" operator in a "having" clause. This is similar to SQL's "having aggregation < value",
@@ -69,7 +69,7 @@ public class LessThanHavingSpec extends BaseHavingSpec
   public byte[] getCacheKey()
   {
     final byte[] aggBytes = StringUtils.toUtf8(aggregationName);
-    final byte[] valBytes = Bytes.toArray(Arrays.asList(value));
+    final byte[] valBytes = Bytes.toArray(Collections.singletonList(value));
     return ByteBuffer.allocate(1 + aggBytes.length + valBytes.length)
                      .put(CACHE_KEY)
                      .put(aggBytes)

processing/src/main/java/io/druid/query/metadata/SegmentMetadataQueryRunnerFactory.java

@@ -51,7 +51,7 @@ import io.druid.segment.Segment;
 import org.joda.time.Interval;
 
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.CancellationException;
@@ -110,7 +110,8 @@ public class SegmentMetadataQueryRunnerFactory implements QueryRunnerFactory<Seg
             columns.put(columnName, column);
           }
         }
-        List<Interval> retIntervals = query.analyzingInterval() ? Arrays.asList(segment.getDataInterval()) : null;
+        List<Interval> retIntervals = query.analyzingInterval() ?
+                                      Collections.singletonList(segment.getDataInterval()) : null;
 
         final Map<String, AggregatorFactory> aggregators;
         Metadata metadata = null;
@@ -162,7 +163,7 @@ public class SegmentMetadataQueryRunnerFactory implements QueryRunnerFactory<Seg
         }
 
         return Sequences.simple(
-            Arrays.asList(
+            Collections.singletonList(
                 new SegmentAnalysis(
                     segment.getIdentifier(),
                     retIntervals,

processing/src/main/java/io/druid/query/metadata/metadata/SegmentMetadataQuery.java

@@ -37,7 +37,7 @@ import io.druid.query.spec.QuerySegmentSpec;
 import org.joda.time.Interval;
 
 import java.nio.ByteBuffer;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Map;
@@ -112,7 +112,7 @@ public class SegmentMetadataQuery extends BaseQuery<SegmentAnalysis>
   {
     super(
         dataSource,
-        (querySegmentSpec == null) ? new MultipleIntervalSegmentSpec(Arrays.asList(DEFAULT_INTERVAL))
+        (querySegmentSpec == null) ? new MultipleIntervalSegmentSpec(Collections.singletonList(DEFAULT_INTERVAL))
             : querySegmentSpec,
         false,
         context
@@ -230,7 +230,6 @@ public class SegmentMetadataQuery extends BaseQuery<SegmentAnalysis>
     return bytes.array();
   }
 
-
   @Override
   public Query<SegmentAnalysis> withOverriddenContext(Map<String, Object> contextOverride)
   {

processing/src/main/java/io/druid/query/spec/LegacySegmentSpec.java

@@ -26,6 +26,7 @@ import io.druid.java.util.common.IAE;
 import org.joda.time.Interval;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -39,7 +40,7 @@ public class LegacySegmentSpec extends MultipleIntervalSegmentSpec
     if (intervals instanceof String) {
       intervalStringList = Arrays.asList((((String) intervals).split(",")));
     } else if (intervals instanceof Interval) {
-      intervalStringList = Arrays.asList(intervals.toString());
+      intervalStringList = Collections.singletonList(intervals.toString());
     } else if (intervals instanceof Map) {
       intervalStringList = (List) ((Map) intervals).get("intervals");
     } else if (intervals instanceof List) {

processing/src/main/java/io/druid/query/spec/QuerySegmentSpecs.java

@@ -21,7 +21,7 @@ package io.druid.query.spec;
 
 import org.joda.time.Interval;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -35,7 +35,7 @@ public class QuerySegmentSpecs
 
   public static QuerySegmentSpec create(Interval interval)
   {
-    return create(Arrays.asList(interval));
+    return create(Collections.singletonList(interval));
   }
 
   public static QuerySegmentSpec create(List<Interval> intervals)

processing/src/main/java/io/druid/query/spec/SpecificSegmentSpec.java

@@ -25,7 +25,7 @@ import io.druid.query.QuerySegmentWalker;
 import io.druid.query.SegmentDescriptor;
 import org.joda.time.Interval;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -43,13 +43,13 @@ public class SpecificSegmentSpec implements QuerySegmentSpec
   @Override
   public List<Interval> getIntervals()
   {
-    return Arrays.asList(descriptor.getInterval());
+    return Collections.singletonList(descriptor.getInterval());
   }
 
   @Override
   public <T> QueryRunner<T> lookup(Query<T> query, QuerySegmentWalker walker)
   {
-    return walker.getQueryRunnerForSegments(query, Arrays.asList(descriptor));
+    return walker.getQueryRunnerForSegments(query, Collections.singletonList(descriptor));
   }
 
   public SegmentDescriptor getDescriptor() { return descriptor; }

processing/src/main/java/io/druid/query/timeboundary/TimeBoundaryQuery.java

@@ -37,7 +37,7 @@ import org.joda.time.DateTime;
 import org.joda.time.Interval;
 
 import java.nio.ByteBuffer;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -68,7 +68,7 @@ public class TimeBoundaryQuery extends BaseQuery<Result<TimeBoundaryResultValue>
   {
     super(
         dataSource,
-        (querySegmentSpec == null) ? new MultipleIntervalSegmentSpec(Arrays.asList(MY_Y2K_INTERVAL))
+        (querySegmentSpec == null) ? new MultipleIntervalSegmentSpec(Collections.singletonList(MY_Y2K_INTERVAL))
             : querySegmentSpec,
         false,
         context
@@ -79,7 +79,8 @@ public class TimeBoundaryQuery extends BaseQuery<Result<TimeBoundaryResultValue>
   }
 
   @Override
-  public boolean hasFilters() {
+  public boolean hasFilters()
+  {
     return dimFilter != null;
   }
 

processing/src/main/java/io/druid/segment/IndexIO.java

@@ -94,6 +94,7 @@ import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.util.AbstractList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.List;
@@ -605,14 +606,14 @@ public class IndexIO
                   );
 
                   bitmaps = GenericIndexed.fromIterable(
-                      Iterables.concat(Arrays.asList(theNullSet), bitmaps),
+                      Iterables.concat(Collections.singletonList(theNullSet), bitmaps),
                       bitmapSerdeFactory.getObjectStrategy()
                   );
                 } else {
                   bumpedDictionary = false;
                   bitmaps = GenericIndexed.fromIterable(
                       Iterables.concat(
-                          Arrays.asList(
+                          Collections.singletonList(
                               bitmapFactory
                                   .union(Arrays.asList(theNullSet, bitmaps.get(0)))
                           ),

processing/src/main/java/io/druid/segment/IndexMerger.java

@@ -86,6 +86,7 @@ import java.nio.IntBuffer;
 import java.nio.channels.FileChannel;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.Iterator;
 import java.util.List;
@@ -101,7 +102,7 @@ public class IndexMerger
 {
   private static final Logger log = new Logger(IndexMerger.class);
 
-  protected static final ListIndexed EMPTY_STR_DIM_VAL = new ListIndexed<>(Arrays.asList(""), String.class);
+  protected static final ListIndexed EMPTY_STR_DIM_VAL = new ListIndexed<>(Collections.singletonList(""), String.class);
   protected static final SerializerUtils serializerUtils = new SerializerUtils();
   protected static final int INVALID_ROW = -1;
   protected static final Splitter SPLITTER = Splitter.on(",");

processing/src/main/java/io/druid/segment/StringDimensionMergerV9.java

@@ -64,14 +64,14 @@ import java.io.IOException;
 import java.nio.IntBuffer;
 import java.nio.MappedByteBuffer;
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 public class StringDimensionMergerV9 implements DimensionMergerV9<int[]>
 {
   private static final Logger log = new Logger(StringDimensionMergerV9.class);
 
-  protected static final ListIndexed EMPTY_STR_DIM_VAL = new ListIndexed<>(Arrays.asList(""), String.class);
+  protected static final ListIndexed EMPTY_STR_DIM_VAL = new ListIndexed<>(Collections.singletonList(""), String.class);
   protected static final int[] EMPTY_STR_DIM_ARRAY = new int[]{0};
   protected static final Splitter SPLITTER = Splitter.on(",");
 

processing/src/main/java/io/druid/segment/data/BlockLayoutLongSupplierSerializer.java

@@ -23,7 +23,6 @@ import com.google.common.io.ByteSink;
 import com.google.common.io.ByteStreams;
 import com.google.common.io.CountingOutputStream;
 import com.google.common.primitives.Ints;
-
 import io.druid.collections.ResourceHolder;
 import io.druid.collections.StupidResourceHolder;
 import io.druid.java.util.common.io.smoosh.FileSmoosher;
@@ -62,7 +61,7 @@ public class BlockLayoutLongSupplierSerializer implements LongSupplierSerializer
   {
     this.ioPeon = ioPeon;
     this.sizePer = writer.getBlockSize(CompressedPools.BUFFER_SIZE);
-    this.flattener = new GenericIndexedWriter<ResourceHolder<ByteBuffer>>(
+    this.flattener = new GenericIndexedWriter<>(
         ioPeon,
         filenameBase,
         VSizeCompressedObjectStrategy.getBufferForOrder(

processing/src/main/java/io/druid/segment/data/CompressedIntsIndexedWriter.java

@@ -75,14 +75,14 @@ public class CompressedIntsIndexedWriter extends SingleValueIndexedIntsWriter
   public CompressedIntsIndexedWriter(
       final int chunkFactor,
       final CompressedObjectStrategy.CompressionStrategy compression,
-      GenericIndexedWriter<ResourceHolder<IntBuffer>> flattner
+      GenericIndexedWriter<ResourceHolder<IntBuffer>> flattener
   )
   {
     this.chunkFactor = chunkFactor;
     this.compression = compression;
     this.endBuffer = IntBuffer.allocate(chunkFactor);
     this.numInserted = 0;
-    this.flattener = flattner;
+    this.flattener = flattener;
   }
 
   @Override

processing/src/main/java/io/druid/segment/data/CompressedVSizeIntsIndexedSupplier.java

@@ -357,7 +357,7 @@ public class CompressedVSizeIntsIndexedSupplier implements WritableSupplier<Inde
     /**
      * Returns the value at the given index in the current decompression buffer
      *
-     * @param index index of the value in the curent buffer
+     * @param index index of the value in the current buffer
      *
      * @return the value at the given index
      */

processing/src/main/java/io/druid/segment/data/GenericIndexedWriter.java

@@ -391,7 +391,6 @@ public class GenericIndexedWriter<T> implements Closeable
       }
       writeHeaderLong(smoosher, headerFile, bagSizePower, buffer);
     }
-
   }
 
   public void writeToChannel(WritableByteChannel channel, FileSmoosher smoosher) throws IOException
@@ -403,7 +402,8 @@ public class GenericIndexedWriter<T> implements Closeable
     }
   }
 
-  private void writeHeaderLong(FileSmoosher smoosher, RandomAccessFile headerFile, int bagSizePower, byte[] buffer) throws IOException
+  private void writeHeaderLong(FileSmoosher smoosher, RandomAccessFile headerFile, int bagSizePower, byte[] buffer)
+      throws IOException
   {
     ByteBuffer helperBuffer = ByteBuffer.allocate(Ints.BYTES).order(ByteOrder.nativeOrder());
 

processing/src/main/java/io/druid/segment/data/IndexedIntsIterator.java

@@ -30,7 +30,7 @@ public class IndexedIntsIterator extends AbstractIntIterator
   private final IndexedInts baseInts;
   private final int size;
 
-  int currIndex = 0;
+  private int currIndex = 0;
 
   public IndexedIntsIterator(
       IndexedInts baseInts
@@ -48,7 +48,8 @@ public class IndexedIntsIterator extends AbstractIntIterator
   }
 
   @Override
-  public int nextInt() {
+  public int nextInt()
+  {
     return baseInts.get(currIndex++);
   }
 

processing/src/main/java/io/druid/segment/data/VSizeIndexedWriter.java

@@ -116,16 +116,11 @@ public class VSizeIndexedWriter extends MultiValueIndexedIntsWriter implements C
         numBytesWritten < Integer.MAX_VALUE, "Wrote[%s] bytes, which is too many.", numBytesWritten
     );
 
-    OutputStream metaOut = ioPeon.makeOutputStream(metaFileName);
+    try (OutputStream metaOut = ioPeon.makeOutputStream(metaFileName)) {
-
-    try {
       metaOut.write(new byte[]{VERSION, numBytesForMax});
       metaOut.write(Ints.toByteArray((int) numBytesWritten + 4));
       metaOut.write(Ints.toByteArray(numWritten));
     }
-    finally {
-      metaOut.close();
-    }
   }
 
   public InputSupplier<InputStream> combineStreams()
@@ -133,8 +128,8 @@ public class VSizeIndexedWriter extends MultiValueIndexedIntsWriter implements C
     return ByteStreams.join(
         Iterables.transform(
             Arrays.asList(metaFileName, headerFileName, valuesFileName),
-            new Function<String,InputSupplier<InputStream>>() {
+            new Function<String, InputSupplier<InputStream>>()
-
+            {
               @Override
               public InputSupplier<InputStream> apply(final String input)
               {

processing/src/main/java/io/druid/segment/incremental/IncrementalIndex.java

@@ -70,6 +70,7 @@ import java.io.Closeable;
 import java.lang.reflect.Array;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.Deque;
 import java.util.Iterator;
@@ -868,9 +869,9 @@ public abstract class IncrementalIndex<AggregatorType> implements Iterable<Row>,
             public Object apply(@Nullable Object input)
             {
               if (input == null || Array.getLength(input) == 0) {
-                return Arrays.asList("null");
+                return Collections.singletonList("null");
               }
-              return Arrays.asList(input);
+              return Collections.singletonList(input);
             }
           }
       ) + '}';

processing/src/main/java/io/druid/segment/incremental/SpatialDimensionRowTransformer.java

@@ -36,7 +36,7 @@ import io.druid.java.util.common.ISE;
 import io.druid.java.util.common.parsers.ParseException;
 import org.joda.time.DateTime;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -189,7 +189,7 @@ public class SpatialDimensionRowTransformer implements Function<InputRow, InputR
         }
 
         if (spatialDimVals.size() == spatialDim.getDims().size()) {
-          spatialLookup.put(spatialDimName, Arrays.asList(JOINER.join(spatialDimVals)));
+          spatialLookup.put(spatialDimName, Collections.singletonList(JOINER.join(spatialDimVals)));
           finalDims.add(spatialDimName);
         }
       }

processing/src/test/java/io/druid/query/groupby/GroupByQueryRunnerFailureTest.java

@@ -247,7 +247,6 @@ public class GroupByQueryRunnerFailureTest
   @Test(timeout = 10000, expected = InsufficientResourcesException.class)
   public void testInsufficientResourcesOnBroker() throws IOException
   {
-    final ReferenceCountingResourceHolder<List<ByteBuffer>> holder = mergeBufferPool.takeBatch(1, 10);
     final GroupByQuery query = GroupByQuery
         .builder()
         .setDataSource(
@@ -267,10 +266,8 @@ public class GroupByQueryRunnerFailureTest
         .setContext(ImmutableMap.of(QueryContexts.TIMEOUT_KEY, 500))
         .build();
 
-    try {
+    try (ReferenceCountingResourceHolder<List<ByteBuffer>> holder = mergeBufferPool.takeBatch(1, 10)) {
       GroupByQueryRunnerTestHelper.runQuery(factory, runner, query);
-    } finally {
-      holder.close();
     }
   }
 }

processing/src/test/java/io/druid/query/spec/SpecificSegmentQueryRunnerTest.java

@@ -48,7 +48,7 @@ import org.joda.time.Interval;
 import org.junit.Assert;
 import org.junit.Test;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -154,7 +154,7 @@ public class SpecificSegmentQueryRunnerTest
           public Sequence run(QueryPlus queryPlus, Map responseContext)
           {
             return Sequences.withEffect(
-                Sequences.simple(Arrays.asList(value)),
+                Sequences.simple(Collections.singletonList(value)),
                 new Runnable()
                 {
                   @Override

processing/src/test/java/io/druid/segment/IndexMergerV9CompatibilityTest.java

@@ -201,7 +201,6 @@ public class IndexMergerV9CompatibilityTest
     finally {
       if (index != null) {
         index.close();
-        ;
       }
 
       if (outDir != null) {

processing/src/test/java/io/druid/segment/data/CompressedVSizeIndexedV3WriterTest.java

@@ -115,10 +115,9 @@ public class CompressedVSizeIndexedV3WriterTest
   private void checkSerializedSizeAndData(int offsetChunkFactor, int valueChunkFactor) throws Exception
   {
     FileSmoosher smoosher = new FileSmoosher(FileUtils.getTempDirectory());
-    final IOPeon ioPeon = new TmpFileIOPeon();
     final IndexedMultivalue<IndexedInts> indexedMultivalue;
 
-    try {
+    try (IOPeon ioPeon = new TmpFileIOPeon()) {
       int maxValue = vals.size() > 0 ? getMaxValue(vals) : 0;
       CompressedIntsIndexedWriter offsetWriter = new CompressedIntsIndexedWriter(
           ioPeon, "offset", offsetChunkFactor, byteOrder, compressionStrategy
@@ -170,9 +169,6 @@ public class CompressedVSizeIndexedV3WriterTest
       }
       CloseQuietly.close(indexedMultivalue);
     }
-    finally {
-      ioPeon.close();
-    }
   }
 
   int getMaxValue(final List<int[]> vals)
@@ -245,10 +241,9 @@ public class CompressedVSizeIndexedV3WriterTest
         offsetChunkFactor
     )).toFile();
     FileSmoosher smoosher = new FileSmoosher(tmpDirectory);
-    final IOPeon ioPeon = new TmpFileIOPeon();
     int maxValue = vals.size() > 0 ? getMaxValue(vals) : 0;
 
-    try {
+    try (IOPeon ioPeon = new TmpFileIOPeon()) {
       CompressedIntsIndexedWriter offsetWriter = new CompressedIntsIndexedWriter(
           offsetChunkFactor,
           compressionStrategy,
@@ -316,9 +311,6 @@ public class CompressedVSizeIndexedV3WriterTest
       CloseQuietly.close(indexedMultivalue);
       mapper.close();
     }
-    finally {
-      ioPeon.close();
-    }
   }
 
   @Test

server/src/main/java/io/druid/guice/ServerModule.java

@@ -23,7 +23,6 @@ import com.fasterxml.jackson.databind.jsontype.NamedType;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.google.inject.Binder;
 import com.google.inject.Provides;
-
 import io.druid.guice.annotations.Self;
 import io.druid.initialization.DruidModule;
 import io.druid.java.util.common.concurrent.ScheduledExecutorFactory;
@@ -36,7 +35,7 @@ import io.druid.timeline.partition.LinearShardSpec;
 import io.druid.timeline.partition.NumberedShardSpec;
 import io.druid.timeline.partition.SingleDimensionShardSpec;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -61,7 +60,7 @@ public class ServerModule implements DruidModule
   @Override
   public List<? extends com.fasterxml.jackson.databind.Module> getJacksonModules()
   {
-    return Arrays.asList(
+    return Collections.singletonList(
         new SimpleModule()
             .registerSubtypes(
                 new NamedType(SingleDimensionShardSpec.class, "single"),

server/src/main/java/io/druid/server/coordination/ServerManager.java

@@ -68,6 +68,7 @@ import org.joda.time.Interval;
 import javax.annotation.Nullable;
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.ExecutorService;
@@ -381,11 +382,11 @@ public class ServerManager implements QuerySegmentWalker
 
                 final PartitionChunk<ReferenceCountingSegment> chunk = entry.getChunk(input.getPartitionNumber());
                 if (chunk == null) {
-                  return Arrays.<QueryRunner<T>>asList(new ReportTimelineMissingSegmentQueryRunner<T>(input));
+                  return Collections.singletonList(new ReportTimelineMissingSegmentQueryRunner<T>(input));
                 }
 
                 final ReferenceCountingSegment adapter = chunk.getObject();
-                return Arrays.asList(
+                return Collections.singletonList(
                     buildAndDecorateQueryRunner(factory, toolChest, adapter, input, cpuTimeAccumulator)
                 );
               }

server/src/main/java/io/druid/server/coordination/ZkCoordinator.java

@@ -305,7 +305,7 @@ public class ZkCoordinator implements DataSegmentChangeHandler
   }
 
   /**
-   * Load a single segment. If the segment is loaded succesfully, this function simply returns. Otherwise it will
+   * Load a single segment. If the segment is loaded successfully, this function simply returns. Otherwise it will
    * throw a SegmentLoadingException
    *
    * @throws SegmentLoadingException
@@ -606,7 +606,7 @@ public class ZkCoordinator implements DataSegmentChangeHandler
           throw new SegmentLoadingException(e, "Failed to announce segments[%s]", queue);
         }
 
-        // get any exception that may have been thrown in background annoucing
+        // get any exception that may have been thrown in background announcing
         try {
           // check in case intervalMillis is <= 0
           if (startedAnnouncing != null) {

server/src/main/java/io/druid/server/coordinator/LoadQueuePeon.java

@@ -23,7 +23,6 @@ import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.collect.Lists;
 import com.metamx.emitter.EmittingLogger;
-
 import io.druid.java.util.common.ISE;
 import io.druid.java.util.common.concurrent.ScheduledExecutors;
 import io.druid.server.coordination.DataSegmentChangeRequest;
@@ -38,8 +37,8 @@ import org.apache.zookeeper.CreateMode;
 import org.apache.zookeeper.WatchedEvent;
 import org.apache.zookeeper.data.Stat;
 
-import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 import java.util.concurrent.Callable;
@@ -155,7 +154,7 @@ public class LoadQueuePeon
 
     log.info("Asking server peon[%s] to load segment[%s]", basePath, segment.getIdentifier());
     queuedSize.addAndGet(segment.getSize());
-    segmentsToLoad.put(segment, new SegmentHolder(segment, LOAD, Arrays.asList(callback)));
+    segmentsToLoad.put(segment, new SegmentHolder(segment, LOAD, Collections.singletonList(callback)));
   }
 
   public void dropSegment(
@@ -184,7 +183,7 @@ public class LoadQueuePeon
     }
 
     log.info("Asking server peon[%s] to drop segment[%s]", basePath, segment.getIdentifier());
-    segmentsToDrop.put(segment, new SegmentHolder(segment, DROP, Arrays.asList(callback)));
+    segmentsToDrop.put(segment, new SegmentHolder(segment, DROP, Collections.singletonList(callback)));
   }
 
   private void processSegmentChangeRequest() {

server/src/test/java/io/druid/server/coordinator/CostBalancerStrategyBenchmark.java

@@ -71,7 +71,8 @@ public class CostBalancerStrategyBenchmark extends AbstractBenchmark
   }
 
   @AfterClass
-  public static void tearDown(){
+  public static void tearDown()
+  {
     serverHolderList = null;
   }
 

server/src/test/java/io/druid/server/coordinator/helper/DruidCoordinatorCleanupOvershadowedTest.java

@@ -38,7 +38,7 @@ import org.joda.time.DateTime;
 import org.joda.time.Interval;
 import org.junit.Test;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 public class DruidCoordinatorCleanupOvershadowedTest
@@ -63,6 +63,7 @@ public class DruidCoordinatorCleanupOvershadowedTest
                                                            .interval(new Interval(start, start.plusHours(1)))
                                                            .version("2")
                                                            .build();
+
   @Test
   public void testRun()
   {
@@ -70,14 +71,16 @@ public class DruidCoordinatorCleanupOvershadowedTest
     availableSegments = ImmutableList.of(segmentV1, segmentV0, segmentV2);
 
     druidCluster = new DruidCluster(
-        ImmutableMap.of("normal", MinMaxPriorityQueue.orderedBy(Ordering.natural().reverse()).create(Arrays.asList(
+        ImmutableMap.of("normal", MinMaxPriorityQueue.orderedBy(Ordering.natural().reverse()).create(
-            new ServerHolder(druidServer, mockPeon
+            Collections.singletonList(new ServerHolder(druidServer, mockPeon))
-            )))));
+        )));
 
     EasyMock.expect(druidServer.getDataSources())
             .andReturn(ImmutableList.of(druidDataSource))
             .anyTimes();
-    EasyMock.expect(druidDataSource.getSegments()).andReturn(ImmutableSet.<DataSegment>of(segmentV1, segmentV2)).anyTimes();
+    EasyMock.expect(druidDataSource.getSegments())
+            .andReturn(ImmutableSet.<DataSegment>of(segmentV1, segmentV2))
+            .anyTimes();
     EasyMock.expect(druidDataSource.getName()).andReturn("test").anyTimes();
     coordinator.removeSegment(segmentV1);
     coordinator.removeSegment(segmentV0);