Month: March 2009

Obtaining java versions from compiled .class files

salilp java, notes

From http://www.rgagnon.com/javadetails/java-0544.html

The first 4 bytes are a magic number, 0xCAFEBABe, to identify a valid class file then the next 2 bytes identify the class format version (major and minor).

Possible major/minor value : 

major  minor Java platform version 
45       3           1.0
45       3           1.1
46       0           1.2
47       0           1.3
48       0           1.4
49       0           1.5
50       0           1.6

So, all you need to do is, open the .class file in binary mode in a text editor and look at the first 8 bytes.

For e.g., here are the first 8 bytes (hex) from a .class file: CA FE BA BE 00 00 00 30

This makes it a java class compiled either under JDK1.4, or at the very least, compiled with 1.4 compatibility turned on.