java.lang.ExceptionInInitializerError

[huanmoon]

org.bukkit.plugin.InvalidPluginException: java.lang.ExceptionInInitializerError
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:135) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-21fe707-741a1bd]
at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:329) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-21fe707-741a1bd]
at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-21fe707-741a1bd]
at org.bukkit.craftbukkit.v1_8_R3.CraftServer.loadPlugins(CraftServer.java:292) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-21fe707-741a1bd]
at net.minecraft.server.v1_8_R3.DedicatedServer.init(DedicatedServer.java:198) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-21fe707-741a1bd]
at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:525) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-21fe707-741a1bd]
at java.lang.Thread.run(Thread.java:750) [?:1.8.0_402]
Caused by: java.lang.ExceptionInInitializerError
at java.lang.Class.forName0(Native Method) ~[?:1.8.0_402]
at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_402]
at org.bukkit.plugin.java.PluginClassLoader.(PluginClassLoader.java:64) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-21fe707-741a1bd]
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-21fe707-741a1bd]
... 6 more
Caused by: java.lang.NullPointerException
at net.jitse.npclib.NPCLib.(NPCLib.java:29) ~[?:?]
at net.jitse.npclib.NPCLib.(NPCLib.java:68) ~[?:?]
at net.achievevoid.underground.UnderGround.(UnderGround.java:20) ~[?:?]
at java.lang.Class.forName0(Native Method) ~[?:1.8.0_402]
at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_402]
at org.bukkit.plugin.java.PluginClassLoader.(PluginClassLoader.java:64) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-21fe707-741a1bd]
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-21fe707-741a1bd]
... 6 more

it went wrong like this =/