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RE: Branch for generics

From: David Holmes
Subject: RE: Branch for generics
Date: Thu, 12 Aug 2004 08:16:42 +1000

Matthias writes:
> And a remark to the conditions: "a majority of VMs" could perhaps really
> mean "a majority of compilers". As far as I remember, the changes in the
> class format used for generics are backward-compatible. Indeed, I had no
> problems to run code using generics and compiled by the javac of the JDK
> 1.5 with the VM of the JDK 1.4.

The may be just the luck of a shared code base. The class file format
version number is increased once again for 1.5 (to 49.0) and that means pre
1.5 VMs need not support it. The official definition from Sun is that:

"The Java virtual machine implementation of Sun's JDK release 1.0.2 supports
class file format versions 45.0 through 45.3 inclusive. Sun's JDK releases
1.1.X can support class file formats of versions in the range 45.0 through
45.65535 inclusive. For  k >= 2 implementations of version 1.k of the Java 2
platform can support class file formats of versions in the range 45.0
through 44+k.0 inclusive."

So Sun's JDK 1.4 VM is not required to support 1.5 class files. Of course it
is up to the individual non-Sun VM's whether they will be able to load such
class files and simply ignore the extra information that is now present.
Remember that more than generics has changed the class file format.

David Holmes

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