address comments

Author: brwe

core/src/main/java/org/elasticsearch/common/lucene/search/function/FiltersFunctionScoreQuery.java

@@ -37,6 +37,8 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.Objects;
@@ -238,7 +240,7 @@ public Explanation explain(LeafReaderContext context, int doc) throws IOExceptio
             } else {
                 // it is a little weird to add a match although no function matches but that is the way function_score behaves right now
                 factorExplanation = Explanation.match(1.0f,
-                    "No function matched", new ArrayList<>());
+                    "No function matched", Collections.emptyList());
             }
             expl = combineFunction.explain(expl, factorExplanation, maxBoost);
             if (minScore != null && minScore > expl.getValue()) {

core/src/test/java/org/elasticsearch/index/query/functionscore/FunctionScoreTests.java

@@ -733,22 +733,22 @@ public void testExplanationAndScoreEqualsEvenIfNoFunctionMatches() throws IOExce
         CombineFunction combineFunction = randomFrom(new
             CombineFunction[]{CombineFunction.SUM, CombineFunction.AVG, CombineFunction.MIN, CombineFunction.MAX,
             CombineFunction.MULTIPLY, CombineFunction.REPLACE});
-        
+
         // check for document that has no macthing function
         FiltersFunctionScoreQuery query = new FiltersFunctionScoreQuery(new TermQuery(new Term(FIELD, "out")), scoreMode,
             new FilterFunction[]{new FilterFunction(new TermQuery(new Term("_uid", "2")), new WeightFactorFunction(10))},
             Float.MAX_VALUE, Float.NEGATIVE_INFINITY, combineFunction);
         TopDocs searchResult = localSearcher.search(query, 1);
-        Explanation exp1 = localSearcher.explain(query, searchResult.scoreDocs[0].doc);
-        assertThat(searchResult.scoreDocs[0].score, equalTo(exp1.getValue()));
+        Explanation explanation = localSearcher.explain(query, searchResult.scoreDocs[0].doc);
+        assertThat(searchResult.scoreDocs[0].score, equalTo(explanation.getValue()));
 
         // check for document that has a matching function
         query = new FiltersFunctionScoreQuery(new TermQuery(new Term(FIELD, "out")), scoreMode,
             new FilterFunction[]{new FilterFunction(new TermQuery(new Term("_uid", "1")), new WeightFactorFunction(10))},
             Float.MAX_VALUE, Float.NEGATIVE_INFINITY, combineFunction);
         searchResult = localSearcher.search(query, 1);
-        exp1 = localSearcher.explain(query, searchResult.scoreDocs[0].doc);
-        assertThat(searchResult.scoreDocs[0].score, equalTo(exp1.getValue()));
+        explanation = localSearcher.explain(query, searchResult.scoreDocs[0].doc);
+        assertThat(searchResult.scoreDocs[0].score, equalTo(explanation.getValue()));
     }
 
     private static class DummyScoreFunction extends ScoreFunction {