Re: When to use float (in teaching)
Christian wrote:
Also a situtation where float is preferred for me to double:
A volatile float is written atomic [sic] while a volatile double is =
not!
Lew wrote:
That is totally not true.
Volatile doubles are written atomically. JLS 17.7:
Writes and reads of volatile long and double values are always atomic.
Mark Thornton wrote:
It was true of some early JVMs.
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4023233
Note that despite what it says in that bug report, this has been fixed.
That is so 20th century!
Note that the memory model changed significantly (with Java 5) also,
in particular with respect to the semantics of 'volatile'.
I think it's safe to challenge on the basis of the JLS an incorrect
statement about Java semantics irrespective of bugs that were fixed
years and years ago. The point is that Sun's JVM and presumably every
other one extant today conforms to the language specification
regarding atomic reads and writes of volatile longs and doubles.
As Java developers we have to go by the specification, not by bugs in
its implementations. Those that rely on violations of the
specification risk having their code break when the bug is fixed, as,
say, Apache commons-lang did in tbeir "enum" implementation prior to
Java 5 that broke when Sun fixed the bug (and Apache refused to fix
it). Java programmers have a right to expect Java implementations to
conform to the specification.
That is moot here, anyway, since volatile actually works as specified
in this matter: reads and writes of volatile longs and doubles are
atomic. To state otherwise does a huge disservice to those who might
not know better.
--
Lew