Checking emtpty item stack crashes with null pointer exception

[Roboguy99]

I'm trying to make my machine fill buckets if you put them in a certain slot, so I want to check that there is a bucket in the slot, however my if statement crashes with a null pointer exception when I load into the game with my current method.

 

 

It crashes on this line on what I assume is the first check.

if(slotBucketOut.getItem() == Items.bucket && (this.distilledWater - 1000) >= 0)

 

Here is all of my code in that class:

 

  Reveal hidden contents

 

package roboguy99.foodTech.common.tile;

import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.init.Blocks;
import net.minecraft.init.Items;
import net.minecraft.inventory.IInventory;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import roboguy99.foodTech.common.tile.prefab.Tile;

public class TileDistiller extends Tile implements IInventory
{
protected ItemStack[] slot = new ItemStack[4];
private String customName;
private static final int MAX_WATER = 10000;
private static final int PROCESS_TIME = 200;
public int water = 0;
public int distilledWater = 0;
public int processTimeRemaining;
public int timeSpentProcessing;
private int furnaceBurnTime = 0;
private int temperature;

@Override
public void updateEntity()
{
	boolean shouldMarkDirty = false;

	ItemStack slotBucketIn = this.getStackInSlot(0);
	ItemStack slotFuel = this.getStackInSlot(1);
	ItemStack slotSalt = this.getStackInSlot(2);
	ItemStack slotBucketOut = this.getStackInSlot(3);

	if(slotFuel != null && this.getBurnTime(slotFuel.getItem()) > 0 && !this.isBurning())
	{
		slotFuel.stackSize--;
		this.furnaceBurnTime = this.getBurnTime(slotFuel.getItem());
		shouldMarkDirty = true;

		if(slotFuel.stackSize == 0)
		{
			slotFuel = null;
			this.setInventorySlotContents(1, null);
			shouldMarkDirty = true;
		}
	}

	if(slotBucketIn != null && slotBucketIn.getItem() == Items.water_bucket && (this.water + 1000) <= MAX_WATER)
	{
		slotBucketIn = null;
		this.setInventorySlotContents(0, null);

		this.water += 1000;

		this.setInventorySlotContents(0, new ItemStack(Items.bucket));
	}

	if(this.temperature > 100 && this.isBurning() && this.water > 0 && this.distilledWater < MAX_WATER)
	{
		this.water--;
		this.distilledWater++;

		if(this.processTimeRemaining == 0)
		{
			if (slotSalt == null) this.setInventorySlotContents(3, new ItemStack(roboguy99.foodTech.common.item.Items.itemSalt));
			else slotSalt.stackSize++;

			this.processTimeRemaining = TileDistiller.PROCESS_TIME;
		}
	}

	if(slotBucketOut.getItem() == Items.bucket && (this.distilledWater - 1000) >= 0)
	{
		slotBucketOut = null;
		this.setInventorySlotContents(3, null);

		this.distilledWater -= 1000;

		this.setInventorySlotContents(3, new ItemStack(roboguy99.foodTech.common.item.Items.itemBucketDistilledWater));
	}

	this.temperature--;
	this.processTimeRemaining--;
	if(this.furnaceBurnTime > 0) this.furnaceBurnTime--;
	if(this.temperature < 300) this.temperature++;
	if(shouldMarkDirty) this.markDirty();
}

private int getBurnTime(Item item)
{
	if(item == Items.coal) return 1600;
	if(item == Item.getItemFromBlock(Blocks.coal_block)) return 16000;
	return 0;
}

private boolean isBurning()
{
	return this.furnaceBurnTime > 0;
}

@Override
public ItemStack decrStackSize(int i, int j) 
{
		if(this.slot[i] != null)
		{
			ItemStack itemStack;

			if(this.slot[i].stackSize <= j)
			{
				itemStack = this.slot[i];
				this.slot[i] = null;
				return itemStack;
			}
			else
			{
				itemStack = this.slot[i].splitStack(j);

				if(this.slot[i].stackSize == 0)
				{
					this.slot[i] = null;
					this.setInventorySlotContents(i, null);
				}

				return itemStack;
			}
		}

	return null;
}

public ItemStack getStackInSlot(int i) 
{
	return this.slot[i];
}

public ItemStack getStackInSlotOnClosing(int i) 
{
	if(this.slot[i] != null)
	{
		ItemStack itemStack = this.slot[i];
		this.slot[i] = null;
		return itemStack;
	}

	return null;
}

public boolean isItemValidForSlot(int slot, ItemStack itemStack)
{
	return slot == 2 ? false : true;
}

public boolean isUseableByPlayer(EntityPlayer entityPlayer) 
{
	return true;
}

public void setInventorySlotContents(int i, ItemStack itemStack) 
{
	this.slot[i] = itemStack;

	if(itemStack != null && itemStack.stackSize > this.getInventoryStackLimit())
	{
		itemStack.stackSize = this.getInventoryStackLimit();
	}
}

public boolean canExtractItem(int i, ItemStack var2, int j) 
{
	return true;
}

public boolean canInsertItem(int slot, ItemStack itemStack, int side) 
{
	return this.isItemValidForSlot(slot, itemStack);
}

public int[] getAccessibleSlotsFromSide(int i) 
{
	return null;
}

public String getInventoryName() 
{
	return this.hasCustomInventoryName() ? this.customName : "container.threeSlotMachine";
}

public boolean hasCustomInventoryName() 
{
	return this.customName != null && this.customName.length() > 0;
}

public int getInventoryStackLimit() 
{
	return 64;
}

public int getSizeInventory() 
{
	return this.slot.length;
}

public void openInventory() {}
public void closeInventory() {}
}

 

 

 

If anyone can help I'd greatly appreciate it, thanks.

[Roboguy99]

  On 11/9/2014 at 7:22 PM, diesieben07 said:

The ItemStack will be

null

if the slot is empty. You need to check for that, as you can't call methods on references that are

null

.

 

Ok, would that just be

if(slotBucketOut != null)