注册监听器抛出NullPointerException

Question

我正在尝试使用Bukkit PingAPI在客户端服务器列表上创建一个假玩家计数器，但它一直在抛出NullPointerExceptions

这是我的代码

package mpolder;

import org.bukkit.plugin.java.JavaPlugin;
import skionz.pingapi.PingAPI;
import skionz.pingapi.PingEvent;
import skionz.pingapi.PingListener;


public class fakePlayer
        extends JavaPlugin
        implements PingListener {

    @Override
    public void onEnable() {
        PingAPI.registerListener(new PingListener() {
            public void onPing(PingEvent event) {
                event.getReply().setOnlinePlayers(5000);
            }
        });

    }


    @Override
    public void onPing(PingEvent event) {
        event.getReply().setOnlinePlayers(5000);
    }
}

这是堆栈跟踪

java.lang.NullPointerException
    at skionz.pingapi.PingAPI.registerListener(PingAPI.java:26) ~[?:?]
    at mpolder.fakePlayer.onEnable(fakePlayer.java:19) ~[?:?]
    at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:316) ~[spigot_server.jar:git-Spigot-1544]
    at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:329) [spigot_server.jar:git-Spigot-1544]
    at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:405) [spigot_server.jar:git-Spigot-1544]
    at org.bukkit.craftbukkit.v1_7_R4.CraftServer.loadPlugin(CraftServer.java:476) [spigot_server.jar:git-Spigot-1544]
    at org.bukkit.craftbukkit.v1_7_R4.CraftServer.enablePlugins(CraftServer.java:394) [spigot_server.jar:git-Spigot-1544]
    at org.bukkit.craftbukkit.v1_7_R4.CraftServer.reload(CraftServer.java:866) [spigot_server.jar:git-Spigot-1544]
    at org.bukkit.Bukkit.reload(Bukkit.java:301) [spigot_server.jar:git-Spigot-1544]
    at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:23) [spigot_server.jar:git-Spigot-1544]
    at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:181) [spigot_server.jar:git-Spigot-1544]
    at org.bukkit.craftbukkit.v1_7_R4.CraftServer.dispatchCommand(CraftServer.java:767) [spigot_server.jar:git-Spigot-1544]
    at org.bukkit.craftbukkit.v1_7_R4.CraftServer.dispatchServerCommand(CraftServer.java:753) [spigot_server.jar:git-Spigot-1544]
    at net.minecraft.server.v1_7_R4.DedicatedServer.aB(DedicatedServer.java:326) [spigot_server.jar:git-Spigot-1544]
    at net.minecraft.server.v1_7_R4.DedicatedServer.v(DedicatedServer.java:290) [spigot_server.jar:git-Spigot-1544]
    at net.minecraft.server.v1_7_R4.MinecraftServer.u(MinecraftServer.java:584) [spigot_server.jar:git-Spigot-1544]
    at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:490) [spigot_server.jar:git-Spigot-1544]
    at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [spigot_server.jar:git-Spigot-1544]