The specifications of the `substring`, `subSequence`, and `toString` methods of the `StringBuilder` and `StringBuffer` classes have been modified not to require a new `String` instance to be returned every time. This allows implementations to improve performance by returning an already-existing string, such as the empty string, when that is appropriate. In all cases, a `String` containing the expected value will be returned. However, applications should not depend on these methods to return a *new* `String` instance every time.