Java_exception if the thread is interruptedexchange_time e x t u is similar to exchange e x, except that the
current thread will at most wait for t (time value whose unit is
u); see
exchange(...).Java_exception if the thread is interruptedJava_exception if time has elapsed with no exchangewrap obj wraps the reference obj into an option type:Some x if obj is not null;None if obj is null.unwrap obj unwraps the option obj into a bare reference:Some x is mapped to x;None is mapped to null.