[14:35:03] [Server thread/ERROR]: Could not load 'plugins/Medipack.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: de/simon/medipack/main/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 org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:133) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
	at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:327) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
	at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:248) [spigot.jar:git-Spigot-dcd1643-e60fc34]
	at org.bukkit.craftbukkit.v1_12_R1.CraftServer.loadPlugins(CraftServer.java:305) [spigot.jar:git-Spigot-dcd1643-e60fc34]
	at net.minecraft.server.v1_12_R1.DedicatedServer.init(DedicatedServer.java:205) [spigot.jar:git-Spigot-dcd1643-e60fc34]
	at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:545) [spigot.jar:git-Spigot-dcd1643-e60fc34]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_242]
Caused by: java.lang.UnsupportedClassVersionError: de/simon/medipack/main/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_242]
	at java.lang.ClassLoader.defineClass(ClassLoader.java:757) ~[?:1.8.0_242]
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.8.0_242]
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:148) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:100) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:419) ~[?:1.8.0_242]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:352) ~[?:1.8.0_242]
	at java.lang.Class.forName0(Native Method) ~[?:1.8.0_242]
	at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_242]
	at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:78) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:129) ~[spigot.jar:git-Spigot-dcd1643-e60fc34]
	... 6 more