Java

We currently run Java 17.

JDK Installation

Ubuntu

OpenJDK is the recommended JDK to install.

OpenJDK

Use apt to install openjdk-17-jdk, openjdk-17-doc, openjdk-17-source:

# apt install openjdk-17-jdk openjdk-17-doc openjdk-17-source

Verify installation by opening a terminal and typing

java -version

sdk install java 17.0.3-zulu

~/.sdkman/candidates/java/17.0.3-zulu

Jetbrains Runtime

The Jetbrains runtime (customized JDK) is an option for installing on Linux. It provides font rendering fixes. Read more here.

Manual Azul Zulu JDK

Manually install Azul's Zulu JDK:

$ curl -sL https://cdn.azul.com/zulu/bin/zulu17.34.19-ca-jdk17.0.3-linux_x64.tar.gz -o zulu.tar.gz
$ tar -xvzf zulu.tar.gz
# mv zulu17.34.19-ca-jdk17.0.3-linux_x64/ /opt/.
# rm /opt/zulu
# ln -s /opt/zulu17.34.19-ca-jdk17.0.3-linux_x64/ /opt/zulu

Windows

Oracle (recommended)

Download installer from https://www.oracle.com/java/technologies/downloads/#java17. The x64 MSI installer is the most convenient. Default installation settings are fine.

Verify installation. Open a terminal and call

java -version

Something like the following should be outputted:

java version "17.0.3.1" 2022-04-22 LTS
Java(TM) SE Runtime Environment (build 17.0.3.1+2-LTS-6)
Java HotSpot(TM) 64-Bit Server VM (build 17.0.3.1+2-LTS-6, mixed mode, sharing)

Aside: java will be installed at the location

C:\Program Files\Java

Azul

Azul is providing JDK 17 with JavaFX as part of their community Zulu distribution. You may also reference the official Zulu Installation Guide including the Installation on Windows Using the Zulu ZIP File page.

1. Visit https://www.azul.com/downloads/zulu-community/?architecture=x86-64-bit&package=jdk-fx
2. Under Zulu Community Downloads, select:
   1. Java Version: Java 17 (LTS)
   2. Operating System: Windows
   3. Java Package: JDK FX (if not already selected)
3. Download the zip distribution and extract the contents to a temporary folder
4. Move the extracted folder to something like C:\Program Files\Zulu\zulu17.34.19-ca-fx-jdk17.0.3-win_x64
5. In Windows > System Properties > Environment Variables
   
   1. Append the bin directory of the JDK to the PATH variable (i.e PATH=<other_stuff>;C:\Program Files\Zulu\zulu17.34.19-ca-fx-jdk17.0.3-win_x64\bin)
   2. Under System Variables, set JAVA_HOME to the JDK directory (i.e JAVA_HOME=;C:\Program Files\Zulu\zulu17.34.19-ca-fx-jdk17.0.3-win_x64). Move it to the top of the list if you have multiple versions
6. Make sure you configure your IDE settings to reference this JDK. There will probably be 2 references - the Java compiler and the gradle compiler
7. (Optional) Open a new console and check that java -version prints something like the following

java -version
openjdk version "17.0.3" 2022-04-19 LTS
OpenJDK Runtime Environment Zulu17.34+19-CA (build 17.0.3+7-LTS)
OpenJDK 64-Bit Server VM Zulu17.34+19-CA (build 17.0.3+7-LTS, mixed mode, sharing)

Note: JDKs are also available from https://adoptopenjdk.net/, but they won't provide JavaFX, which breaks most of IHMC's robotics software.

Mac OS X

Download JDK and JavaFX from https://adoptopenjdk.net/ or https://www.azul.com/downloads/zulu/zulufx/

Download JavaFX 17 from https://www.azul.com/downloads/zulu-community/zulufx/

Configuration

Logging

See the IHMC Log Tools README for details on enabling different log levels.

Testing

For testing in IDE, see /wiki/spaces/HOWTO/pages/14288377. For testing with Gradle and on Bamboo, see IHMC CI Gradle plugin and /wiki/spaces/HOWTO/pages/14288249.

JVM options

Increase Stack Size

Use -Xss4m for example to set a custom stack size. Default is 512 KB (-Xss512k)

Increase Heap Size

To set maximum heap size use for example -Xmx512m or -Xmx2g.

To set initial heap size use for example -Xms512m or -Xms1g.

Non-standard options

Use java -X  to print out your specific version of Java's non-standard options. They are hard to find online because they are can be different for each JDK version. For example, here are the options for OpenJDK 1.8.0_232:

$ java -X
    -Xmixed           mixed mode execution (default)
    -Xint             interpreted mode execution only
    -Xbootclasspath:<directories and zip/jar files separated by :>
                      set search path for bootstrap classes and resources
    -Xbootclasspath/a:<directories and zip/jar files separated by :>
                      append to end of bootstrap class path
    -Xbootclasspath/p:<directories and zip/jar files separated by :>
                      prepend in front of bootstrap class path
    -Xdiag            show additional diagnostic messages
    -Xnoclassgc       disable class garbage collection
    -Xincgc           enable incremental garbage collection
    -Xloggc:<file>    log GC status to a file with time stamps
    -Xbatch           disable background compilation
    -Xms<size>        set initial Java heap size
    -Xmx<size>        set maximum Java heap size
    -Xss<size>        set java thread stack size
    -Xprof            output cpu profiling data
    -Xfuture          enable strictest checks, anticipating future default
    -Xrs              reduce use of OS signals by Java/VM (see documentation)
    -Xcheck:jni       perform additional checks for JNI functions
    -Xshare:off       do not attempt to use shared class data
    -Xshare:auto      use shared class data if possible (default)
    -Xshare:on        require using shared class data, otherwise fail.
    -XshowSettings    show all settings and continue
    -XshowSettings:all
                      show all settings and continue
    -XshowSettings:vm show all vm related settings and continue
    -XshowSettings:properties
                      show all property settings and continue
    -XshowSettings:locale
                      show all locale related settings and continue

The -X options are non-standard and subject to change without notice.

-XX Options

For a list, see The most complete list of -XX options for Java JVM.

Realtime

The IHMC Realtime project contains documentation about IHMC's realtime Java configuration.

More pages:

• /wiki/spaces/OSS/pages/17367046
• /wiki/spaces/OSS/pages/17367048.

Java Platform Module System

See Java Platform Module System

Learning Resources

• Guide: Learning Java
• The Java™ Tutorials
• Thinking in Java (ISBN 978-0131872486) by Bruce Eckel

See also

• YourKit Java Profiler
• List of new features since Java 8
• Java Platform Module System
• JAR-compatible File and Resource handling
• Guide: Learning Java