code: @SafeVarargs
      public static <E> void addAll(Collection<E> collection, E[]... arr) {
          if (collection == null) {
              throw new IllegalArgumentException("collection cannot be null");
          }
          for (E[] oarr : arr) {
              for (E o : oarr) {
                  collection.add(o);
              }
          }
      }
docs: Adds the contents of one or more arrays to a collection.
  
  @param collection a {@link Collection}. Cannot be <code>null</code>.
  @param arr zero or more <code>E[]</code>.