CharSequence.subSequence optimizations

[Pavel Rappo]

Hi,

While working with an API that extensively uses java.lang.CharSequence, I've
noticed most JDK implementations of CharSequence do not optimize for corner
cases in CharSequence.subSequence(int start, int end). Namely,

    1. start == end (an empty subsequence)
    2. start == 0 && end == CharSequence.this.length() (the same sequence)

It seems to be a valid solution to return a shared empty sequence object and the
same (this) sequence in the first and the second case respectively.

I wonder if it's worth investigating pros and cons of introducing these
optimizations. Thanks.

P.S. If it's a known issue, I would appreciate if somebody provided a link to a
relevant discussion.

-Pavel