For that to be possible, either you had to cast from mutable to immutable (which you shouldn't have) or the mutable string derives from the immutable string (which it shouldn't have). The latter ...

Extent-local variables would provide a way to share data both within a thread and with child threads in Java, making it easier to reason about data flow.

The object-oriented paradigm popularized by languages including Java and C++ has slowly given way to a functional programming approach that is advocated by popular Python libraries and JavaScript ...