Returns a lexicographic-order comparator with a function that extracts a long sort key.

Parameters:

keyExtractor

the function used to extract the long sort key

Returns:  a lexicographic-order comparator composed of this and then the long sort key

Exceptions:

NullPointerException

if the argument is null.

See also:
comparingLong(ToLongFunction), thenComparing(Comparator)

Since:  1.8

@implSpec This default implementation behaves as if thenComparing(comparingLong(keyExtractor)).