Re: How to find out from *.class file with which Java version 1.6
or 1.5 it was compiled?
On 08/04/2010 10:21 AM, 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?
If you have the file utility on your computer, file knows about Java
version numbers:
$ file Review.class
Review.class: compiled Java class data, version 50.0 (Java 1.6)
If you don't, here is a brief overview of the class header format:
$ hd Review.class
00000000 ca fe ba be 00 00 00 32 00 78 0a 00 28 00 47 09
^^^^^^^^^^^ ^^^^^ ^^^^^
magic minor major
The magic number is always 0xCAFEBABE: this is what tells the JVM that
the following file is a Java class file. The major file number is a
16-bit short. Version 50 corresponds to 6, 49 to 5, 48 to 1.4, 47 1.3,
46 1.2, and 45 1.1 or lower. The minor file number is only used in
practice for 1.0 versus 1.1 detection (I believe 1.1 is actually 45.3,
but don't quote me on that).
Any more precise versioning is not reified into the class files; in
general, it should not matter.
--
Beware of bugs in the above code; I have only proved it correct, not
tried it. -- Donald E. Knuth