Don't use 'p' as a parameter name prefix (we don't do that anywhere

else.)

Add missing Javadoc.

src/main/java/org/apache/commons/lang3/Streams.java

@@ -439,8 +439,8 @@ public class Streams {
         private static final Set<Characteristics> characteristics = Collections.emptySet();
         private final Class<O> elementType;
 
-        public ArrayCollector(final Class<O> pElementType) {
-            elementType = pElementType;
+        public ArrayCollector(final Class<O> elementType) {
+            this.elementType = elementType;
         }
 
         @Override