The Collections.addAll method javadoc currently states:
/**
     * Adds all of the specified elements to the specified collection.
     * Elements to be added may be specified individually or as an array.
     * The behaviour of this convenience method is similar to that of
     * {@code cc.addAll(Collections.unmodifiableList(Arrays.asList(elements)))}.

...

It seems that the "cc" in that line should instead have been "c" since the param passed to this method is named "c" and the rest of the API specification in this javadoc uses "c".