Development Assistance Error with CraftPlayer

Trying to finish a plugin for a request, and I get an error when trying to get a player's ping. I'd like to say that the version that the server is running is different from the one the plugin is using, but I honestly have no clue.

Error (open) Error (close)

Code:

16.01 15:19:54 [Server] INFO ... 15 more 16.01 15:19:54 [Server] INFO at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_65] 16.01 15:19:54 [Server] INFO at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_65] 16.01 15:19:54 [Server] INFO at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_65] 16.01 15:19:54 [Server] INFO at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_65] 16.01 15:19:54 [Server] INFO at com.bizarreplatinum.staffstick.StaffStick.onInteractEntity(StaffStick.java:65) ~[?:?] 16.01 15:19:54 [Server] INFO at com.bizarreplatinum.staffstick.StaffStick.getPing(StaffStick.java:94) ~[?:?] 16.01 15:19:54 [Server] INFO Caused by: java.lang.NoClassDefFoundError: org/bukkit/craftbukkit/v1_8_R1/entity/CraftPlayer 16.01 15:19:54 [Server] INFO at java.lang.Thread.run(Thread.java:745) [?:1.8.0_65] 16.01 15:19:54 [Server] INFO at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:614) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:711) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:378) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:772) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at net.minecraft.server.v1_8_R3.SystemUtils.a(SourceFile:44) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_65] 16.01 15:19:54 [Server] INFO at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_65] 16.01 15:19:54 [Server] INFO at net.minecraft.server.v1_8_R3.PlayerConnectionUtils$1.run(SourceFile:13) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at net.minecraft.server.v1_8_R3.PacketPlayInUseEntity.a(SourceFile:11) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at net.minecraft.server.v1_8_R3.PacketPlayInUseEntity.a(SourceFile:52) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at net.minecraft.server.v1_8_R3.PlayerConnection.a(PlayerConnection.java:1318) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:310) ~[PaperSpigot-1.8.8.jar:git-PaperSpigot-d709888-d3e0b6f] 16.01 15:19:54 [Server] INFO org.bukkit.event.EventException 16.01 15:19:54 [Server] ERROR Could not pass event PlayerInteractAtEntityEvent to StaffStick v1.0

Method (open) Method (close)

Code:

public int getPing(Player p) {
        CraftPlayer cp = (CraftPlayer) p;
        EntityPlayer ep = cp.getHandle();
        return ep.ping;
    }