Re: How to find out from *.class file with which Java version 1.6 or
1.5 it was compiled?
Gianni Galore wrote:
Assume I got a *.class file.
Is there a way to find out with which java version (e.g. 1.5upd14 or v1.6.upd20) this *.class
file was previously compiled?
<http://java.sun.com/docs/books/jvms/second_edition/html/
ClassFile.doc.html>
The first four bytes of the class file comprise the magic number
0xCAFEBABE (unsigned int).
The next two bytes comprise the minor version number of the class file
format (unsigned short).
The next two bytes comprise the major version number of the class file
format (unsigned short).
The major and minor versions tell you what version of Java can run the
class file, but not necessarily which version produced it. I don't
know of any way to get at the Java version that compiled it, but you
can live without that information anyway.
Class file formats do not change between minor Java version updates,
and not even necessarily between major Java version updates.
You should know that Java 5u14 and 6u20 lack certain critical bug and
security fixes and you should upgrade to the latest available versions
of those products, updates 22 and 21, respectively. (Java 5 has been
frozen for public use at update 22, having reached its end-of-service-
life on November 3, 2009, though paying customers can get more recent
updates. Yes, that's right, Java 5 has been officially obsolete for
nine months, a fact that your customers who are only just now
upgrading from their obsolete 8 1/2-year-old version to the obsolete
nearly-6-year-old version really should find out.)
You can find which major class file versions correspond to which Java
versions at
<http://mindprod.com/jgloss/javaclassformat.html>
--
Lew