pmcserver requires java 25

[WildPenquin]

Hi,

Current development version of papermc requires java version 25. The docker image only ships with 21.

$ java --version
openjdk 21.0.10 2026-01-20
OpenJDK Runtime Environment (build 21.0.10+7-Ubuntu-124.04)
OpenJDK 64-Bit Server VM (build 21.0.10+7-Ubuntu-124.04, mixed mode, sharing)

$ cat /app/log/console/pmcserver-console.log 
Starting org.bukkit.craftbukkit.Main
Exception in thread "ServerMain" java.lang.UnsupportedClassVersionError: org/bukkit/craftbukkit/Main has been compiled by a more recent version of the Java Runtime (class file version 69.0), this version of the Java Runtime only recognizes class file versions up to 65.0
        at java.base/java.lang.ClassLoader.defineClass1(Native Method)
        at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1027)
        at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
        at java.base/java.net.URLClassLoader.defineClass(URLClassLoader.java:524)
        at java.base/java.net.URLClassLoader$1.run(URLClassLoader.java:427)
        at java.base/java.net.URLClassLoader$1.run(URLClassLoader.java:421)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:714)
        at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:420)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:593)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
        at java.base/java.lang.Class.forName0(Native Method)
        at java.base/java.lang.Class.forName(Class.java:536)
        at java.base/java.lang.Class.forName(Class.java:515)
        at io.papermc.paperclip.Paperclip.lambda$main$0(Paperclip.java:38)
        at java.base/java.lang.Thread.run(Thread.java:1583)

Workaround: temporarily, just upgrade to openjdk25.

$ apt install openjdk-25-jre-headless

But at next restart of the docker image, the newer java version will be gone.