Minimum java version on

[amirAtWork]

On main page it reads "Note: You need Java 17 installed to run Fake SMTP Server." but I can't start with a later version.

[root@server system]# /opt/jdk-20.0.1/bin/java -XX:MaxRAMPercentage=90.0 -jar /opt/fake-smtp-server/fake-smtp-server-2.2.0.jar
Exception in thread "main" java.lang.UnsupportedClassVersionError: de/gessnerfl/fakesmtp/Application has been compiled by a more recent version of the Java Runtime (class file version 65.0), this version of the Java Runtime only recognizes class file versions up to 64.0
at java.base/java.lang.ClassLoader.defineClass1(Native Method)
at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1013)
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:588)
at org.springframework.boot.loader.net.protocol.jar.JarUrlClassLoader.loadClass(JarUrlClassLoader.java:104)
at org.springframework.boot.loader.launch.LaunchedClassLoader.loadClass(LaunchedClassLoader.java:91)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:496)
at java.base/java.lang.Class.forName(Class.java:475)
at org.springframework.boot.loader.launch.Launcher.launch(Launcher.java:88)
at org.springframework.boot.loader.launch.Launcher.launch(Launcher.java:53)
at org.springframework.boot.loader.launch.JarLauncher.main(JarLauncher.java:58)

[root@server system]# /opt/jdk-20.0.1/bin/java -version
openjdk version "20.0.1" 2023-04-18
OpenJDK Runtime Environment (build 20.0.1+9-29)
OpenJDK 64-Bit Server VM (build 20.0.1+9-29, mixed mode, sharing)

[gessnerfl]

@amirAtWork indeed I missed to update the required Java version with the recent release 2.2.0. Starting with this release Java 21 is required. The README is now updated accordingly.