# What Java Version Are You Running? > Did you know there are multiple ways you check your Java version and even get much more information than you might think, very quickly? - URL: https://foojay.io/today/what-java-version-are-you-running-lets-take-a-look-under-the-hood-of-the-jdk/ - Published: 2022-12-15 - Authors: Frank Delporte - Categories: Java Core, Tutorials From time to time, you need to check which Java version is installed on your computer or server, for instance when starting on a new project or configuring an application to run on a server. But did you know there are multiple ways you can do this and even get much more information than you might think, very quickly? Let's find out... ## Reading the Java Version in the Terminal Probably the easiest way to find the installed version is by using the `java -version` terminal command: ``` $ java -version openjdk version "19" 2022-09-20 OpenJDK Runtime Environment Zulu19.28+81-CA (build 19+36) OpenJDK 64-Bit Server VM Zulu19.28+81-CA (build 19+36, mixed mode, sharing) ``` ## Checking Version Files in the Installation Directory The above output results from info read by the `java` executable from a file inside its installation directory. Let's explore what we can find there. On my machine, as I use [SDKMAN](https://sdkman.io/) to switch between different Java versions, all my versions are stored here: ``` $ ls -l /Users/frankdelporte/.sdkman/candidates/java/ total 0 drwxr-xr-x 15 frankdelporte staff 480 Apr 17 2022 11.0.15-zulu drwxr-xr-x 16 frankdelporte staff 512 Apr 17 2022 17.0.3.fx-zulu drwxr-xr-x 15 frankdelporte staff 480 Mar 29 2022 18.0.1-zulu drwxr-xr-x 15 frankdelporte staff 480 Sep 7 18:36 19-zulu drwxr-xr-x 18 frankdelporte staff 576 Apr 18 2022 8.0.332-zulu lrwxr-xr-x 1 frankdelporte staff 7 Nov 21 21:09 current -> 19-zulu ``` And in each of these directories a release file can be found which also shows us the version information, including some extra information. ``` $ cat /Users/frankdelporte/.sdkman/candidates/java/19-zulu/release IMPLEMENTOR="Azul Systems, Inc." IMPLEMENTOR_VERSION="Zulu19.28+81-CA" JAVA_VERSION="19" JAVA_VERSION_DATE="2022-09-20" LIBC="default" MODULES="java.base java.compiler ... jdk.unsupported jdk.unsupported.desktop jdk.xml.dom" OS_ARCH="aarch64" OS_NAME="Darwin" SOURCE=".:git:3d665268e905" $ cat /Users/frankdelporte/.sdkman/candidates/java/8.0.332-zulu//release JAVA_VERSION="1.8.0_332" OS_NAME="Darwin" OS_VERSION="11.2" OS_ARCH="aarch64" SOURCE="git:f4b2b4c5882e" ``` ## Getting More Information With showSettings In 2010, an experimental flag (indicated with the `X`) was added to OpenJDK to provide more configuration information: `-XshowSettings`. ![](Screenshot-2022-12-01-at-12.23.11.png) Twitter screenshot of a message by OpenJDK about adding the -XshowSettings flag This flag can be called with different arguments, each producing an other information output. The cleanest way to call this flag, is by adding `-version`, otherwise you will get the long Java manual output as no application code was found to be executed. ### Reading the System Properties By using the `-XshowSettings:properties` flag, a long list of various properties is shown. ``` $ java -XshowSettings:properties -version Property settings: file.encoding = UTF-8 file.separator = / ftp.nonProxyHosts = local|*.local|169.254/16|*.169.254/16 http.nonProxyHosts = local|*.local|169.254/16|*.169.254/16 java.class.path = java.class.version = 63.0 java.home = /Users/frankdelporte/.sdkman/candidates/java/19-zulu/zulu-19.jdk/Contents/Home java.io.tmpdir = /var/folders/np/6j1kls013kn2gpg_k6tz2lkr0000gn/T/ java.library.path = /Users/frankdelporte/Library/Java/Extensions /Library/Java/Extensions /Network/Library/Java/Extensions /System/Library/Java/Extensions /usr/lib/java . java.runtime.name = OpenJDK Runtime Environment java.runtime.version = 19+36 java.specification.name = Java Platform API Specification java.specification.vendor = Oracle Corporation java.specification.version = 19 java.vendor = Azul Systems, Inc. java.vendor.url = http://www.azul.com/ java.vendor.url.bug = http://www.azul.com/support/ java.vendor.version = Zulu19.28+81-CA java.version = 19 java.version.date = 2022-09-20 java.vm.compressedOopsMode = Zero based java.vm.info = mixed mode, sharing java.vm.name = OpenJDK 64-Bit Server VM java.vm.specification.name = Java Virtual Machine Specification java.vm.specification.vendor = Oracle Corporation java.vm.specification.version = 19 java.vm.vendor = Azul Systems, Inc. java.vm.version = 19+36 jdk.debug = release line.separator = \n native.encoding = UTF-8 os.arch = aarch64 os.name = Mac OS X os.version = 13.0.1 path.separator = : socksNonProxyHosts = local|*.local|169.254/16|*.169.254/16 stderr.encoding = UTF-8 stdout.encoding = UTF-8 sun.arch.data.model = 64 sun.boot.library.path = /Users/frankdelporte/.sdkman/candidates/java/19-zulu/zulu-19.jdk/Contents/Home/lib sun.cpu.endian = little sun.io.unicode.encoding = UnicodeBig sun.java.launcher = SUN_STANDARD sun.jnu.encoding = UTF-8 sun.management.compiler = HotSpot 64-Bit Tiered Compilers user.country = BE user.dir = /Users/frankdelporte user.home = /Users/frankdelporte user.language = en user.name = frankdelporte openjdk version "19" 2022-09-20 OpenJDK Runtime Environment Zulu19.28+81-CA (build 19+36) OpenJDK 64-Bit Server VM Zulu19.28+81-CA (build 19+36, mixed mode, sharing) ``` If you ever faced the problem of an unsupported Java version 59 (are similar), you'll now also understand where this value is defined, it's right here in this list as `java.class.version`. It's an internal number used by Java to define the version. | | | | | | | | | | | | | | |-------------------|----|----|----|----|----|----|----|----|----|----|----|----| | **Java release** | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | | **Class version** | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | ### Reading the Locale Information In case you didn't know yet, I live in Belgium and use English as my computer language, as you can see when using the `-XshowSettings:locale` flag: ``` $ java -XshowSettings:locale -version Locale settings: default locale = English (Belgium) default display locale = English (Belgium) default format locale = English (Belgium) available locales = , af, af_NA, af_ZA, af_ZA_#Latn, agq, agq_CM, agq_CM_#Latn, ak, ak_GH, ak_GH_#Latn, am, am_ET, am_ET_#Ethi, ar, ar_001, ar_AE, ar_BH, ar_DJ, ar_DZ, ar_EG, ar_EG_#Arab, ar_EH, ar_ER, ... zh_MO_#Hant, zh_SG, zh_SG_#Hans, zh_TW, zh_TW_#Hant, zh__#Hans, zh__#Hant, zu, zu_ZA, zu_ZA_#Latn openjdk version "19" 2022-09-20 OpenJDK Runtime Environment Zulu19.28+81-CA (build 19+36) OpenJDK 64-Bit Server VM Zulu19.28+81-CA (build 19+36, mixed mode, sharing) ``` ### Reading the VM Settings With the `-XshowSettings:vm` flag, some info is shown about the Java Virtual Machine. As you can see in the second example, the amount of maximum heap memory size can be defined with the `-Xmx` flag. ``` $ java -XshowSettings:vm -version VM settings: Max. Heap Size (Estimated): 8.00G Using VM: OpenJDK 64-Bit Server VM openjdk version "19" 2022-09-20 OpenJDK Runtime Environment Zulu19.28+81-CA (build 19+36) OpenJDK 64-Bit Server VM Zulu19.28+81-CA (build 19+36, mixed mode, sharing) $ java -XshowSettings:vm -Xmx512M -version VM settings: Max. Heap Size: 512.00M Using VM: OpenJDK 64-Bit Server VM openjdk version "19" 2022-09-20 OpenJDK Runtime Environment Zulu19.28+81-CA (build 19+36) OpenJDK 64-Bit Server VM Zulu19.28+81-CA (build 19+36, mixed mode, sharing) ``` ### Reading all at Once If you want all of the information above with one call, use the `-XshowSettings:all` flag. ## Conclusion Next to `java -version`, we can also use `java -XshowSettings:all -version` to get more info about our Java environment.