Solved Error on console.

A few days ago there was a problem after which, all the new plugins that I want to write do not work.
The console shows an error:

[01:17:54 ERROR]: Could not load 'plugins\GrandProtect.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError
: ru/GrandProtect/Main has been compiled by a more recent version of the Java Ru
ntime (class file version 54.0), this version of the Java Runtime only recognize
s class file versions up to 52.0
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.j
ava:131) ~[patched_1.12.2.jar:git-Paper-1618]
at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.
java:329) ~[patched_1.12.2.jar:git-Paper-1618]
at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager
.java:251) ~[patched_1.12.2.jar:git-Paper-1618]
at org.bukkit.craftbukkit.v1_12_R1.CraftServer.loadPlugins(CraftServer.j
ava:318) ~[patched_1.12.2.jar:git-Paper-1618]
at net.minecraft.server.v1_12_R1.DedicatedServer.init(DedicatedServer.ja
va:222) ~[patched_1.12.2.jar:git-Paper-1618]
at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.jav
a:616) ~[patched_1.12.2.jar:git-Paper-1618]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_271]
Caused by: java.lang.UnsupportedClassVersionError: ru/GrandProtect/Main has been
compiled by a more recent version of the Java Runtime (class file version 54.0)
, this version of the Java Runtime only recognizes class file versions up to 52.
0
at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.8.0_271]
at java.lang.ClassLoader.defineClass(Unknown Source) ~[?:1.8.0_271]
at java.security.SecureClassLoader.defineClass(Unknown Source) ~[?:1.8.0
_271]
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.
java:152) ~[patched_1.12.2.jar:git-Paper-1618]
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.
java:104) ~[patched_1.12.2.jar:git-Paper-1618]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_271]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_271]
at java.lang.Class.forName0(Native Method) ~[?:1.8.0_271]
at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_271]
at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.jav
a:82) ~[patched_1.12.2.jar:git-Paper-1618]
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.j
ava:127) ~[patched_1.12.2.jar:git-Paper-1618]
... 6 more

 

Did you change the version the server was running on?
Did you write something else to GrandProject.jar?
Maybe the plugin is too big and you need to update your and the server Java version to allow the bigger files to be compiled.


These are some parts that I found interesting in the log message:

PS: I'm not a professional java user, this are just my assumptions about the problem

 

@MrKoLoTeR
You are compiling with a different version of Java than the server.

 

How can I solve this problem in more detail?

Thanks, but no, I have not changed the version on which the server was running and the plugin is not large

Thanks, but no, I have not changed the version on which the server was running and the plugin is not large.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

@MrKoLoTeR
Change the version of Java you are compiling with to be the same version that the server is running.

 

For version until 1.16 you need to compile in Java 1.8 , for 1.17 and beyond you need at least Java 1.11, or something like that

 

Thank you!