Java

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Last updated: Sept 11, 2024 by Dexton Anderson
5 min read

We currently run Java 17.

Contents

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

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

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

Needs updating for Java 17.

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:

Java Platform Module System

See Java Platform Module System

Learning Resources

See also