Fail fast in ArrayCollector constructor.
diff --git a/src/main/java/org/apache/commons/lang3/stream/Streams.java b/src/main/java/org/apache/commons/lang3/stream/Streams.java
index b564ff9..fd981e6 100644
--- a/src/main/java/org/apache/commons/lang3/stream/Streams.java
+++ b/src/main/java/org/apache/commons/lang3/stream/Streams.java
@@ -20,6 +20,7 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 import java.util.Set;
 import java.util.function.BiConsumer;
 import java.util.function.BinaryOperator;
@@ -81,7 +82,7 @@
          * @param elementType The element type.
          */
         public ArrayCollector(final Class<O> elementType) {
-            this.elementType = elementType;
+            this.elementType = Objects.requireNonNull(elementType, "elementType");
         }
 
         @Override