length property

int length

Returns the number of objects in this list.

The valid indices for a list are 0 through length - 1.

Implementation 

int get length => _source.length;
void length= (int newLength)
inherited

This operation is not supported by an unmodifiable list.

Implementation 

set length(int newLength) {
  throw new UnsupportedError(
      "Cannot change the length of an unmodifiable list");
}