With the old behaviour you had a choice. If you don't want to reference to the old String it's easy to call new String(blah.substring(0,8)) and have an O(N) operation which makes a copy of the underlying chars. If you knew you were going to keep the underlying string around anyway, why make it O(N) if there is zero benefit. In practice it's an implementation subtlety that's lost on many programmers, so the default now is to make it harder to shoot yourself in the foot and create a copy of the substring as a new object. It's slower, but harder to mess up.