The number of objects in this list.
The valid indices for a list are
length - 1.
int get length;
Changes the length of this list.
newLength is greater than
the current length, entries are initialized to
Increasing the length fails if the element type does not allow
Throws an UnsupportedError if the list is fixed-length or
if attempting tp enlarge the list when
null is not a valid element.
set length(int newLength);