Solved Why the hell is this ItemStack null??

I am just confused. Why is

Code:

inventory.getContents();

giving me itemstacks that are literally null??
I am trying to make a plugin that allows players to stack all the same items into one stack. Here is my code
Getting how much items the player has in total:

Code:

public int getAmount(PlayerInventory pi, Material m){
        int r = 0;
        ItemStack[] is = pi.getContents();
        for (ItemStack i : is){
            if (i != null){
                if (i.getType() == m){
                    r += i.getAmount();
                }
            }
        }
        return r;
    }

removing items:

Code:

    public void remove(PlayerInventory pi, Material m, int amount){
        int leftamount = amount;
        ItemStack[] is = pi.getContents();
        for (ItemStack i : is){
            if (i != null){
                if (i.getType() == m){
                    if (i.getAmount() > leftamount){
                        i.setAmount(i.getAmount() - leftamount);
                        break;
                    }
                    if (i.getAmount() < leftamount){
                        leftamount = leftamount - i.getAmount();
                        pi.remove(i);
                    }
                    if (i.getAmount() == leftamount){
                        pi.remove(i);
                        break;
                    }
                }
            }
        }
    }

stacking the items:

Code:

public void stack(PlayerInventory pi, Material m, Player p){
        int amount = getAmount(pi, m) - 1;
        remove(pi, m, amount);
        pi.addItem(new ItemStack(m, amount));
        p.updateInventory();
    }

Here's the error:

Code:

[15:08:41 ERROR]: Could not pass event AsyncPlayerChatEvent to MMOGame v1.0
org.bukkit.event.EventException at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.ja
va:297) ~[craftbukkit.jar:git-Bukkit-3fc97ff] at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.jav
a:62) ~[craftbukkit.jar:git-Bukkit-3fc97ff] at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.j
ava:501) [craftbukkit.jar:git-Bukkit-3fc97ff] at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.j
ava:483) [craftbukkit.jar:git-Bukkit-3fc97ff] at net.minecraft.server.v1_8_R1.PlayerConnection.chat(PlayerConnection.j
ava:983) [craftbukkit.jar:git-Bukkit-3fc97ff] at net.minecraft.server.v1_8_R1.PlayerConnection.a(PlayerConnection.java
:933) [craftbukkit.jar:git-Bukkit-3fc97ff] at net.minecraft.server.v1_8_R1.PacketPlayInChat.a(SourceFile:37) [craft
bukkit.jar:git-Bukkit-3fc97ff] at net.minecraft.server.v1_8_R1.PacketPlayInChat.a(SourceFile:9) [craftb
ukkit.jar:git-Bukkit-3fc97ff] at net.minecraft.server.v1_8_R1.NetworkManager.a(NetworkManager.java:75)
[craftbukkit.jar:git-Bukkit-3fc97ff] at net.minecraft.server.v1_8_R1.NetworkManager.channelRead0(NetworkManag
er.java:236) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChanne
lInboundHandler.java:103) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(Abst
ractChannelHandlerContext.java:332) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(Abstra
ctChannelHandlerContext.java:318) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessage
Decoder.java:163) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(Abst
ractChannelHandlerContext.java:332) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(Abstra
ctChannelHandlerContext.java:318) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessage
Decoder.java:163) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(Abst
ractChannelHandlerContext.java:332) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(Abstra
ctChannelHandlerContext.java:318) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessage
Decoder.java:163) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(Abst
ractChannelHandlerContext.java:332) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(Abstra
ctChannelHandlerContext.java:318) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.handler.timeout.ReadTimeoutHandler.channelRead(ReadTimeoutHa
ndler.java:150) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(Abst
ractChannelHandlerContext.java:332) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(Abstra
ctChannelHandlerContext.java:318) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChanne
lPipeline.java:787) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(Abstra
ctNioByteChannel.java:125) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.jav
a:507) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEve
ntLoop.java:464) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.ja
va:378) [craftbukkit.jar:git-Bukkit-3fc97ff] at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:350) [craftbu
kkit.jar:git-Bukkit-3fc97ff] at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThread
EventExecutor.java:116) [craftbukkit.jar:git-Bukkit-3fc97ff] at java.lang.Thread.run(Unknown Source) [?:1.8.0_73]
Caused by: java.lang.NullPointerException at org.bukkit.inventory.ItemStack.<init>(ItemStack.java:68) ~[craftbukki
t.jar:git-Bukkit-3fc97ff]
        at mmo.game.MMOGame.stack(MMOGame.java:418) ~[?:?]
        at mmo.game.MMOGame.chat(MMOGame.java:684) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_73]
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_73]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_73]
        at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_73]
        va:295) ~[craftbukkit.jar:git-Bukkit-3fc97ff]
        ... 32 more

I've added

Code:

 if (itemstack != null) 

because if is not there i get an Nullpointer Exception telling me that i can't do anything with an ItemStack that is null.
(Also no items are getting added or deleted)
Line 418:

Code:

pi.addItem(new ItemStack(m, amount));

out of the Method

Code:

stack(PlayerInventory pi, Material m, Player p)

The AsyncChatEvent is what triggeres it all:

Code:

if (e.getMessage().equalsIgnoreCase("stack")){
            stack(e.getPlayer().getInventory(), getCoins(e.getPlayer()), e.getPlayer());
        }

 

ItemStacks are null when they are empty. If you're getting the contents of an inventory, there are bound to be quite a few of those.

 

Solved thank you for helping @thapengwin

 

@RoflFrankoc
It seems to me that you're using an AsyncPlayerChatEvent to change some in-game variables, which I'm pretty sure is not thread-safe. What I would recommend doing is scheduling a sync task to run your code in.