[17:12:06 ERROR]: Could not load 'plugins/EG-Core.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: main class `pl.koiczek.Core' does not extend JavaPlugin
        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:74) ~[PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:129) ~[PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:331) ~[PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:254) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.loadPlugins(CraftServer.java:293) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.reload(CraftServer.java:767) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at org.bukkit.Bukkit.reload(Bukkit.java:556) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:25) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:146) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchCommand(CraftServer.java:666) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at net.minecraft.server.v1_8_R3.PlayerConnection.handleCommand(PlayerConnection.java:1189) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at net.minecraft.server.v1_8_R3.PlayerConnection.a(PlayerConnection.java:1001) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(PacketPlayInChat.java:45) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(PacketPlayInChat.java:1) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at net.minecraft.server.v1_8_R3.PlayerConnectionUtils$1.run(SourceFile:13) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_112]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_112]
        at net.minecraft.server.v1_8_R3.SystemUtils.a(SourceFile:44) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:774) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:378) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:713) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:616) [PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        at java.lang.Thread.run(Thread.java:745) [?:1.8.0_112]
Caused by: java.lang.ClassCastException: class pl.koiczek.Core
        at java.lang.Class.asSubclass(Class.java:3404) ~[?:1.8.0_112]
        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:72) ~[PaperSpigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-PaperSpigot-"4c7641d"]
        ... 22 more