How do I detect which kind of JRE is installed — 32bit vs. 64bit

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The JVM architecture in use can be retrieved using the “os.arch” property:

System.getProperty("os.arch");

The “os” part seems to be a bit of a misnomer, or perhaps the original designers did not expect JVMs to be running on architectures they weren’t written for. Return values seem to be inconsistent.

The NetBeans Installer team are tackling the issue of JVM vs OS architecture. Quote:

x64 bit : Java and System

Tracked as the Issue 143434.

Currently we using x64 bit of JVM to
determine if system (and thus
Platform.getHardwareArch()) is 64-bit
or not. This is definitely wrong since
it is possible to run 32bit JVM on
64bit system. We should find a
solution to check OS real 64-bitness
in case of running on 32-bit JVM.

  • for Windows it can be done using WindowsRegistry.IsWow64Process()
  • for Linux – by checking ‘uname -m/-p’ == x86_64
  • for Solaris it can be done using e.g. ‘isainfo -b’
  • for Mac OSX it can’t be done using uname arguments, probably it can be
    solved by creating of 64-bit binary
    and executing on the platform…
    (unfortunately, this does not work:(
    I’ve created binary only with x86_64
    and ppc64 arch and it was successfully
    executed on Tiger..)
  • for Generic Unix support – it is not clear as well… likely checking
    for the same ‘uname -m/-p”https://stackoverflow.com/”getconf
    LONG_BIT’ and comparing it with some
    possible 64-bit values (x86_64, x64,
    amd64, ia64).

Sample properties from different JVMs all running on 64bit Ubuntu 8.0.4:

32bit IBM 1.5:

java.vendor=IBM Corporation
java.vendor.url=http://www.ibm.com/
java.version=1.5.0
java.vm.info=J2RE 1.5.0 IBM J9 2.3 Linux x86-32 j9vmxi3223-20061001 (JIT enabled)
J9VM - 20060915_08260_lHdSMR
JIT  - 20060908_1811_r8
GC   - 20060906_AA
java.vm.name=IBM J9 VM
java.vm.specification.name=Java Virtual Machine Specification
java.vm.specification.vendor=Sun Microsystems Inc.
java.vm.specification.version=1.0
java.vm.vendor=IBM Corporation
java.vm.version=2.3
os.arch=x86
os.name=Linux
os.version=2.6.24-23-generic
sun.arch.data.model=32

64bit Sun 1.6:

java.vendor=Sun Microsystems Inc.
java.vendor.url=http://java.sun.com/
java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport.cgi
java.version=1.6.0_05
java.vm.info=mixed mode
java.vm.name=Java HotSpot(TM) 64-Bit Server VM
java.vm.specification.name=Java Virtual Machine Specification
java.vm.specification.vendor=Sun Microsystems Inc.
java.vm.specification.version=1.0
java.vm.vendor=Sun Microsystems Inc.
java.vm.version=10.0-b19
os.arch=amd64
os.name=Linux
os.version=2.6.24-23-generic
sun.arch.data.model=64

64bit GNU 1.5:

java.vendor=Free Software Foundation, Inc.
java.vendor.url=http://gcc.gnu.org/java/
java.version=1.5.0
java.vm.info=GNU libgcj 4.2.4 (Ubuntu 4.2.4-1ubuntu3)
java.vm.name=GNU libgcj
java.vm.specification.name=Java(tm) Virtual Machine Specification
java.vm.specification.vendor=Sun Microsystems Inc.
java.vm.specification.version=1.0
java.vm.vendor=Free Software Foundation, Inc.
java.vm.version=4.2.4 (Ubuntu 4.2.4-1ubuntu3)
os.arch=x86_64
os.name=Linux
os.version=2.6.24-23-generic

(The GNU version does not report the “sun.arch.data.model” property; presumably other JVMs don’t either.)

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