Java Upgrade for JMRI

After the 4.26 production release of JMRI (which should happen very soon since it's now at 4.25.8) the developers will require you to upgrade Java to version 11. Azul Software's JRE is one of the recommended upgrade packages. This is based on the OpenJDK software and includes choices for both a JDK (software development kit) and a JRE (runtime environment). The vast majority of users will only need the JRE.

<Update 2026-03-12>
The recommended (not required) version of AZUL Java is now 21. DO NOT install 25 unless you are running the JMRI test releases of 5.15.4 or later.

It is available on the Azul downloads page.  Once there scroll down to the list of JREs and JDKs. You can select Java Version, Operating System, Architecture and Package to install. An example is shown in Fig 1. Windows users should select the "JRE" and the ".msi" package. This is the auto-installer. 

Fig 1 Azul selections

<Update 2026-03-09>

If you're not sure of what processor architecture you computer has do the following:

1. Press Windows key and R key simultaneously
2. Type cmd
3. In the cmd window type "echo %PROCESSOR_ARCHITECTURE%" without the quotes
4. You will see AMD64 (which is x86) or the equivalent identifier for your machine
5. Choose that architecture

The author has had this Java v21 installed for some time now and has encountered no problems. It also appears to be slightly faster than the Oracle version.

<CAUTION!>

It is recommended to completely remove your current Java version before performing the upgrade. Some people have had strange results if they do not. If you are using Oracle's Java they have a tool to remove it completely, It is located here.

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