public static <T> List<T> nCopies (int n, T o)

Returns an immutable list consisting of n copies of the specified object. The newly allocated data object is tiny (it contains a single reference to the data object). This method is useful in combination with the List.addAll method to grow lists. The returned list is serializable.

Parameters:
<T>    the class of the object to copy and of the objects in the returned list.
n    the number of elements in the returned list.
o    the element to appear repeatedly in the returned list.

Returns:  an immutable list consisting of n copies of the specified object.

Exceptions:
IllegalArgumentException    if n < 0

See also:
List.addAll(Collection), List.addAll(int, Collection)