Hi,

I am trying to replace diamond swords with a custom item when they are in a player's inventory, but the method ItemStack.getItem() is making the game crash. I have the following code so far:

 

@SubscribeEvent
public void onTickEvent(PlayerTickEvent evt){
		for (int i = 0; i < 35; i++){
			if(evt.player.inventory.getStackInSlot(i).getItem() == Items.diamond_sword){
				System.out.println(i);
			}

 

When I open my world, the game generates the following crash report:

 

---- Minecraft Crash Report ----
// Hey, that tickles! Hehehe!

Time: 7/18/14 4:56 PM
Description: Ticking player

java.lang.NullPointerException: Ticking player
at com.eternaldoom.realmsofchaos.ItemReplaceEvent.onTickEvent(ItemReplaceEvent.java:14)
at cpw.mods.fml.common.eventhandler.ASMEventHandler_5_ItemReplaceEvent_onTickEvent_PlayerTickEvent.invoke(.dynamic)
at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:51)
at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:122)
at cpw.mods.fml.common.FMLCommonHandler.onPlayerPreTick(FMLCommonHandler.java:344)
at net.minecraft.entity.player.EntityPlayer.onUpdate(EntityPlayer.java:273)
at net.minecraft.entity.player.EntityPlayerMP.onUpdateEntity(EntityPlayerMP.java:334)
at net.minecraft.network.NetHandlerPlayServer.processPlayer(NetHandlerPlayServer.java:329)
at net.minecraft.network.play.client.C03PacketPlayer.processPacket(C03PacketPlayer.java:37)
at net.minecraft.network.play.client.C03PacketPlayer$C06PacketPlayerPosLook.processPacket(C03PacketPlayer.java:271)
at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:247)
at net.minecraft.network.NetworkSystem.networkTick(NetworkSystem.java:182)
at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:736)
at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:624)
at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:118)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:495)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:762)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
at com.eternaldoom.realmsofchaos.ItemReplaceEvent.onTickEvent(ItemReplaceEvent.java:14)
at cpw.mods.fml.common.eventhandler.ASMEventHandler_5_ItemReplaceEvent_onTickEvent_PlayerTickEvent.invoke(.dynamic)
at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:51)
at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:122)
at cpw.mods.fml.common.FMLCommonHandler.onPlayerPreTick(FMLCommonHandler.java:344)
at net.minecraft.entity.player.EntityPlayer.onUpdate(EntityPlayer.java:273)

-- Player being ticked --
Details:
Entity Type: null (net.minecraft.entity.player.EntityPlayerMP)
Entity ID: 330
Entity Name: Doomturd
Entity's Exact location: 185.46, 80.00, 118.87
Entity's Block location: World: (185,80,118), Chunk: (at 9,5,6 in 11,7; contains blocks 176,0,112 to 191,255,127), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Entity's Momentum: 0.00, -0.08, 0.00
Stacktrace:
at net.minecraft.entity.player.EntityPlayerMP.onUpdateEntity(EntityPlayerMP.java:334)
at net.minecraft.network.NetHandlerPlayServer.processPlayer(NetHandlerPlayServer.java:329)
at net.minecraft.network.play.client.C03PacketPlayer.processPacket(C03PacketPlayer.java:37)
at net.minecraft.network.play.client.C03PacketPlayer$C06PacketPlayerPosLook.processPacket(C03PacketPlayer.java:271)
at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:247)

-- Ticking connection --
Details:
Connection: net.minecraft.network.NetworkManager@1b2a717a
Stacktrace:
at net.minecraft.network.NetworkSystem.networkTick(NetworkSystem.java:182)
at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:736)
at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:624)
at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:118)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:495)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:762)

-- System Details --
Details:
Minecraft Version: 1.7.10
Operating System: Mac OS X (x86_64) version 10.9.4
Java Version: 1.8.0, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 926731496 bytes (883 MB) / 1037959168 bytes (989 MB) up to 1037959168 bytes (989 MB)
JVM Flags: 3 total; -Xincgc -Xmx1024M -Xms1024M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
FML: MCP v9.05 FML v7.10.23.1186 Minecraft Forge 10.13.0.1186 4 mods loaded, 4 mods active
mcp{9.05} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
FML{7.10.23.1186} [Forge Mod Loader] (forgeSrc-1.7.10-10.13.0.1186.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Forge{10.13.0.1186} [Minecraft Forge] (forgeSrc-1.7.10-10.13.0.1186.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
realmsofchaos{Alpha 1.0 pre 1} [Realms of Chaos] (bin) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Player Count: 1 / 8; [EntityPlayerMP['Doomturd'/330, l='ROC', x=185.46, y=80.00, z=118.87]]
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fml,forge'
#@!@# Game crashed! Crash report saved to: #@!@# ./crash-reports/crash-2014-07-18_16.56.13-server.txt

 

Does anyone know what could be causing this? Thanks!

Hi

 

The slot might be empty.  If it is, the stack will be null.  If you call .getItem() on a null, you will get this crash. 

 

This link might be helpful

http://www.terryanderson.ca/debugging/run.html

 

-TGG

Be sure to check if the slot has an item in it before trying to get the said item. Try adding:

 

evt.player.inventory.getStackInSlot(i) != null

 

to your if statement.

 

Hope this helps!

That worked. Thanks guys!