Sun has a Java System property to determine the bitness of the JVM: 32 or 64:
sun.arch.data.model=32 // 32 bit JVM
sun.arch.data.model=64 // 64 bit JVM
You can use
to determine if its 32/64 from the program.
From the Sun HotSpot FAQ:
When writing Java code, how do I distinguish between 32 and 64-bit operation?
There's no public API that allows you to distinguish between 32 and 64-bit operation. Think of 64-bit as just another platform in the write once, run anywhere tradition. However, if you'd like to write code which is platform specific (shame on you), the system property sun.arch.data.modelhas the value "32", "64", or "unknown".
The only good reason is if your java code is dependent upon native libraries and your code needs to determine which version (32 or 64bit) to load on startup.