Code:
[15:46:36 WARN]: org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: net/rayfall/eyesniper2/skrayfall/Core has been compiled by a more recent version of the Java Runtime (class file version 60.0), this version of the Java Runtime only recognizes class file versions up to 52.0
[15:46:36 WARN]: at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:133)
[15:46:36 WARN]: at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:327)
[15:46:36 WARN]: at net.frankheijden.serverutils.bukkit.managers.BukkitPluginManager.loadPluginDescriptions(BukkitPluginManager.java:70)
[15:46:36 WARN]: at net.frankheijden.serverutils.common.managers.AbstractPluginManager.loadPlugins(AbstractPluginManager.java:78)
[15:46:36 WARN]: at net.frankheijden.serverutils.common.commands.CommandServerUtils.handleLoadPlugin(CommandServerUtils.java:191)
[15:46:36 WARN]: at net.frankheijden.serverutils.dependencies.cloud.execution.CommandExecutionHandler.executeFuture(CommandExecutionHandler.java:95)
[15:46:36 WARN]: at net.frankheijden.serverutils.dependencies.cloud.execution.CommandExecutionCoordinator$SimpleCoordinator.coordinateExecution(CommandExecutionCoordinator.java:123)
[15:46:36 WARN]: at net.frankheijden.serverutils.dependencies.cloud.CommandManager.executeCommand(CommandManager.java:189)
[15:46:36 WARN]: at net.frankheijden.serverutils.dependencies.cloud.bukkit.BukkitCommand.execute(BukkitCommand.java:116)
[15:46:36 WARN]: at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141)
[15:46:36 WARN]: at org.bukkit.craftbukkit.v1_12_R1.CraftServer.dispatchCommand(CraftServer.java:648)
[15:46:36 WARN]: at net.minecraft.server.v1_12_R1.PlayerConnection.handleCommand(PlayerConnection.java:1401)
[15:46:36 WARN]: at net.minecraft.server.v1_12_R1.PlayerConnection.a(PlayerConnection.java:1236)
[15:46:36 WARN]: at net.minecraft.server.v1_12_R1.PacketPlayInChat.a(PacketPlayInChat.java:45)
[15:46:36 WARN]: at net.minecraft.server.v1_12_R1.PacketPlayInChat.a(PacketPlayInChat.java:1)
[15:46:36 WARN]: at net.minecraft.server.v1_12_R1.PlayerConnectionUtils$1.run(SourceFile:13)
[15:46:36 WARN]: at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
[15:46:36 WARN]: at java.util.concurrent.FutureTask.run(Unknown Source)
[15:46:36 WARN]: at net.minecraft.server.v1_12_R1.SystemUtils.a(SourceFile:46)
[15:46:36 WARN]: at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:748)
[15:46:36 WARN]: at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406)
[15:46:36 WARN]: at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679)
[15:46:36 WARN]: at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577)
[15:46:36 WARN]: at java.lang.Thread.run(Unknown Source)
[15:46:36 WARN]: Caused by: java.lang.UnsupportedClassVersionError: net/rayfall/eyesniper2/skrayfall/Core has been compiled by a more recent version of the Java Runtime (class file version 60.0), this version of the Java Runtime only recognizes class file versions up to 52.0
[15:46:36 WARN]: at java.lang.ClassLoader.defineClass1(Native Method)
[15:46:36 WARN]: at java.lang.ClassLoader.defineClass(Unknown Source)
[15:46:36 WARN]: at java.security.SecureClassLoader.defineClass(Unknown Source)
[15:46:36 WARN]: at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:148)
[15:46:36 WARN]: at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:100)
[15:46:36 WARN]: at java.lang.ClassLoader.loadClass(Unknown Source)
[15:46:36 WARN]: at java.lang.ClassLoader.loadClass(Unknown Source)
[15:46:36 WARN]: at java.lang.Class.forName0(Native Method)
[15:46:36 WARN]: at java.lang.Class.forName(Unknown Source)
[15:46:36 WARN]: at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:78)
[15:46:36 WARN]: at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:129)
[15:46:36 WARN]: ... 23 more