GIRAPH-1208

closes #80
diff --git a/giraph-core/src/main/java/org/apache/giraph/aggregators/matrix/MatrixSumAggregator.java b/giraph-core/src/main/java/org/apache/giraph/aggregators/matrix/MatrixSumAggregator.java
index 8ed6bd8..f3233d6 100644
--- a/giraph-core/src/main/java/org/apache/giraph/aggregators/matrix/MatrixSumAggregator.java
+++ b/giraph-core/src/main/java/org/apache/giraph/aggregators/matrix/MatrixSumAggregator.java
@@ -32,7 +32,7 @@
    */
   private String name;
   /** Cache the names of the columns */
-  private ArrayList<String> names = new ArrayList<String>();
+  private ArrayList<String> names = new ArrayList<>();
 
   /**
    * Create a new matrix aggregator with the given prefix name for the vector