How can I tell if I m running in 64-bit JVM or 32-bit JVM from within a program

Question

How can I tell if the JVM in which my application runs is 32 bit or 64-bit   Specifically  what functions or properties I can used to detect this within the program

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On Linux  you can get ELF header information by using either of the following two commands   file  YOUR JRE LOCATION HERE  bin java   o p  ELF 64-bit LSB executable  AMD x86-64  version 1  SYSV   for GNU Linux 2 4 0  dynamically linked  uses shared libs   for GNU Linux 2 4 0  not stripped  or  readelf -h  YOUR JRE LOCATION HERE  bin java   grep  Class    o p  Class                              ELF64

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For Windows  you can check the Java home location  If it contains  x86  it is 32-bit otherwise 64-bit   public static boolean is32Bit         val javaHome   System getProperty  java home        return javaHome contains   x86        public static boolean is64Bit         return  is32Bit        Example paths   C  Program Files  x86  Java jdk1 8 0 181 bin java exe   32-bit C  Program Files Java jdk-10 0 2 bin java exe   64-bit   Why care about a Windows only solution   If you need to know which bit version you re running on  you re likely fiddling around with native code on Windows so platform-independence is out of the window anyway

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Under Windows 7 in the  Control Panel  under  Programs   Programs and Features  the 64-bit variants of JRE  amp  JDK are listed with  64-bit  in  parentheses  e g   Java SE Development Kit 7 Update 65  64-Bit     while for the 32-bit variants the variant is not mentioned in parentheses  e g  just  Java SE Development Kit 8 Update 60

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This is the way JNA solves this with Platform is64Bit    https   github com java-native-access jna blob master src com sun jna Platform java   public static final boolean is64Bit             String model   System getProperty  quot sun arch data model quot                                             System getProperty  quot com ibm vm bitmode quot             if  model    null                return  quot 64 quot  equals model                     if   quot x86-64 quot  equals ARCH                  quot ia64 quot  equals ARCH                  quot ppc64 quot  equals ARCH      quot ppc64le quot  equals ARCH                  quot sparcv9 quot  equals ARCH                  quot mips64 quot  equals ARCH      quot mips64el quot  equals ARCH                  quot amd64 quot  equals ARCH                  quot aarch64 quot  equals ARCH                 return true                    return Native POINTER SIZE    8     ARCH   getCanonicalArchitecture System getProperty  quot os arch quot    osType    static String getCanonicalArchitecture String arch  int platform            arch   arch toLowerCase   trim            if   quot powerpc quot  equals arch                 arch    quot ppc quot                     else if   quot powerpc64 quot  equals arch                 arch    quot ppc64 quot                     else if   quot i386 quot  equals arch      quot i686 quot  equals arch                 arch    quot x86 quot                     else if   quot x86 64 quot  equals arch      quot amd64 quot  equals arch                 arch    quot x86-64 quot                        Work around OpenJDK mis-reporting os arch            https   bugs openjdk java net browse JDK-8073139         if   quot ppc64 quot  equals arch   amp  amp   quot little quot  equals System getProperty  quot sun cpu endian quot                   arch    quot ppc64le quot                        Map arm to armel if the binary is running as softfloat build         if  quot arm quot  equals arch   amp  amp  platform    Platform LINUX  amp  amp  isSoftFloat                  arch    quot armel quot                      return arch         static           String osName   System getProperty  quot os name quot            if  osName startsWith  quot Linux quot                  if   quot dalvik quot  equals System getProperty  quot java vm name quot   toLowerCase                       osType   ANDROID                     Native libraries on android must be bundled with the APK                 System setProperty  quot jna nounpack quot    quot true quot                              else                   osType   LINUX                                  else if  osName startsWith  quot AIX quot                  osType   AIX                    else if  osName startsWith  quot Mac quot      osName startsWith  quot Darwin quot                  osType   MAC                    else if  osName startsWith  quot Windows CE quot                  osType   WINDOWSCE                    else if  osName startsWith  quot Windows quot                  osType   WINDOWS                    else if  osName startsWith  quot Solaris quot      osName startsWith  quot SunOS quot                  osType   SOLARIS                    else if  osName startsWith  quot FreeBSD quot                  osType   FREEBSD                    else if  osName startsWith  quot OpenBSD quot                  osType   OPENBSD                    else if  osName equalsIgnoreCase  quot gnu quot                  osType   GNU                    else if  osName equalsIgnoreCase  quot gnu kfreebsd quot                  osType   KFREEBSD                    else if  osName equalsIgnoreCase  quot netbsd quot                  osType   NETBSD                    else               osType   UNSPECIFIED

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I installed 32-bit JVM and retried it again  looks like the following does tell you JVM bitness  not OS arch   System getProperty  os arch        on a 64-bit Linux box     x86  when using 32-bit JVM    amd64  when using 64-bit JVM   This was tested against both SUN and IBM JVM  32 and 64-bit   Clearly  the system property is not just the operating system arch

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If you are using JNA  you can check whether com sun jna Native POINTER SIZE    4  32 bit  or com sun jna Native POINTER SIZE    8  64 bit

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If you re using JNA  you can do thisPlatform is64Bit

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To get the version of JVM currently running the program  System out println Runtime class getPackage   getImplementationVersion

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For certain versions of Java  you can check the bitness of the JVM from the command line with the flags -d32 and -d64     java -help         -d32          use a 32-bit data model if available     -d64          use a 64-bit data model if available   To check for a 64-bit JVM  run     java -d64 -version   If it s not a 64-bit JVM  you ll get this   Error  This Java instance does not support a 64-bit JVM  Please install the desired version    Similarly  to check for a 32-bit JVM  run     java -d32 -version   If it s not a 32-bit JVM  you ll get this   Error  This Java instance does not support a 32-bit JVM  Please install the desired version    These flags were added in Java 7  deprecated in Java 9  removed in Java 10  and no longer available on modern versions of Java

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Complementary info   On a running process you may use  at least with some recent Sun JDK5 6 versions       opt java1 5 bin jinfo -sysprops 14680   grep sun arch data model Attaching to process ID 14680  please wait    Debugger attached successfully  Server compiler detected  JVM version is 1 5 0 16-b02 sun arch data model   32   where 14680 is PID of jvm running the application   os arch  works too   Also other scenarios are supported   jinfo   option   pid jinfo   option   executable core jinfo   option    server-id  remote-hostname-or-IP    However consider also this note    NOTE - This utility is unsupported and may or may not be available in future versions of the JDK  In Windows Systems where dbgent dll is not present   Debugging Tools for Windows  needs to be installed to have these tools working  Also the PATH environment variable should contain the location of jvm dll used by the target process or the location from which the Crash Dump file was produced

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You retrieve the system property that marks the bitness of this JVM with  System getProperty  quot sun arch data model quot     Possible results are    quot 32 quot      32-bit JVM  quot 64 quot      64-bit JVM  quot unknown quot      Unknown JVM  As described in the 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 model has the value  quot 32 quot    quot 64 quot   or  quot unknown quot    An example where this could be necessary is if your Java code depends on native libraries  and you need to determine whether to load the 32- or 64-bit version of the libraries on startup

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Just type java -version in your console   If a 64 bit version is running  you ll get a message like   java version  1 6 0 18  Java TM  SE Runtime Environment  build 1 6 0 18-b07  Java HotSpot TM  64-Bit Server VM  build 16 0-b13  mixed mode    A 32 bit version will show something similar to   java version  1 6 0 41  Java TM  SE Runtime Environment  build 1 6 0 41-b02  Java HotSpot TM  Client VM  build 20 14-b01  mixed mode  sharing    Note Client instead of 64-Bit Server in the third line  The Client Server part is irrelevant  it s the absence of the 64-Bit that matters   If multiple Java versions are installed on your system  navigate to the  bin folder of the Java version you want to check  and type java -version there

[java] How can I tell if I'm running in 64-bit JVM or 32-bit JVM (from within a program)?

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