My custom furnace only save items in slot 0 if slot 0 is empty furnace puts item from slot 1,2 or 3 into slot 0

package com.TheTroop.legendrymod;

import com.TheTroop.legendrymod.Crafting.blockOvenRecipes;

import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.init.Items;
import net.minecraft.inventory.IInventory;
import net.minecraft.inventory.ISidedInventory;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.nbt.NBTTagCompound;
import net.minecraft.nbt.NBTTagList;
import net.minecraft.tileentity.TileEntity;

public class TileEntityblockOven extends TileEntity implements ISidedInventory{

private ItemStack slots[];

public int dualPower;
public int dualCookTime;
public static final int maxPower = 10000;
public static final int mashingSpeed = 100;

private static final int[] slots_top = new int[] {0, 1};
private static final int[] slots_bottom = new int[] {3};
private static final int[] slots_side = new int[] {2};

private String customName;


public TileEntityblockOven() {
	slots = new ItemStack[4];
}

@Override
public int getSizeInventory() {
	return slots.length;
}

@Override
public ItemStack getStackInSlot(int i) {
	return slots[i];
}

@Override
public ItemStack getStackInSlotOnClosing(int i) {
	if (slots[i] != null) {
		ItemStack itemstack = slots[i];
		slots[i] = null;
		return itemstack;
	}else{
		return null;
	}
}



@Override
public void setInventorySlotContents(int i, ItemStack itemstack) {
	slots[i] = itemstack;
	if(itemstack != null && itemstack.stackSize > getInventoryStackLimit()) {
		itemstack.stackSize = getInventoryStackLimit();
	}

}

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

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


@Override
public int getInventoryStackLimit() {
	return 64;
}

@Override
public boolean isUseableByPlayer(EntityPlayer player) {
	if (worldObj.getTileEntity(xCoord, yCoord, zCoord) != this) {
		return false;
	}else{
		return player.getDistanceSq((double)xCoord + 0.5D, (double)yCoord + 0.5D, (double)zCoord + 0.5D) <= 64;
	}
  
}

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

@Override
public boolean isItemValidForSlot(int i, ItemStack itemstack) {
	return i == 2? false : (i == 1 ? hasItemPower(itemstack) : true);
}

public boolean hasItemPower(ItemStack itemstack) {
	return getItemPower(itemstack) > 0;
}

private static int getItemPower (ItemStack itemstack) {
	if (itemstack == null) {
		return 0;
	}else{
		Item item = itemstack.getItem();

		if(item == LegendryMod.Fgem) return 50;
		return 0;
	}
}

public ItemStack decrStackSize(int i, int j) {
	if (slots[i] != null) {
	if (slots[i].stackSize <= j) {
		ItemStack itemstack = slots[i];
		slots[i] = null;
		return itemstack;
	}

	ItemStack itemstack1 = slots[i].splitStack(j);
	if (slots[i].stackSize == 0) {
		slots[i] = null;
	}

	return itemstack1;
	}else{
		return null;
	}
}

public void readFromNBT (NBTTagCompound nbt) {
	super.readFromNBT(nbt);
	NBTTagList list = nbt.getTagList("Items", 10);
	this.slots = new ItemStack[getSizeInventory()];

	for (int i = 0; i < list.tagCount(); ++i) {
		NBTTagCompound nbt1 = (NBTTagCompound)list.getCompoundTagAt(i) ;
		byte b0 =nbt1.getByte("slot");

		if (b0 >= 0 && b0 < slots.length) {
			this.slots[b0] = ItemStack.loadItemStackFromNBT(nbt1);
		}
	}

	dualPower = nbt.getShort("PowerTime");
	dualCookTime = nbt.getShort("CookTime");
}

public void writeToNBT(NBTTagCompound nbt) {
	super.writeToNBT(nbt);
	nbt.setShort("PowerTime", (short)dualPower);
	nbt.setShort("CookTime", (short) dualCookTime);
	NBTTagList list = new NBTTagList();

	for(int i = 0; i < slots.length; i++) {
		if(slots[i] != null) {
			NBTTagCompound nbt1 = new NBTTagCompound();
			nbt1.setByte("Slot", (byte)i);
			slots[i].writeToNBT(nbt1);
			list.appendTag(nbt1);
		}
	}

	nbt.setTag("Items", list);
}


@Override
public int[] getAccessibleSlotsFromSide (int i) {
	return i == 0 ? slots_bottom : (i == 1 ? slots_top : slots_side);
}

@Override
public boolean canInsertItem(int var1, ItemStack itemstack,
		int p_102007_3_) {
	return this.isItemValidForSlot(var1, itemstack);
}

@Override
public boolean canExtractItem(int i, ItemStack itemstack, int j) {
	return j != 0 || i != 1 || itemstack.getItem() == Items.bucket;
}

public int getMasherProgressScaled(int i) {
	return (dualCookTime * i) / this.mashingSpeed;
}

public int getPowerRemainingScaled(int i) {
	return (dualPower * i) / maxPower;
}

private boolean canMash() {

	if (slots[0] == null || slots[1] == null) {
		return false;
	}

	ItemStack itemstack = blockOvenRecipes.getMashingResult(slots[0].getItem(), slots[1].getItem());

	if (itemstack == null) {
		return false;
	}

	if (slots[3] == null) {
		return true;
	}
	if (!slots[3].isItemEqual(itemstack)) {
		return false;
	}
	if (slots[3].stackSize < getInventoryStackLimit() && slots[3].stackSize < slots[3].getMaxStackSize()) {
		return true;
	}else{
		return slots[3].stackSize < itemstack.getMaxStackSize();
	}
}

private void mashItem() {
	if (canMash()) {
		ItemStack itemstack = blockOvenRecipes.getMashingResult(slots[0].getItem(), slots[1].getItem());

		if (slots[3] == null) {
			slots[3] = itemstack.copy();
		}else if (slots[3].isItemEqual(itemstack)) {
			slots[3].stackSize += itemstack.stackSize;
		}

		for (int i = 0; i < 2; i++) {
			if (slots[i].stackSize <= 0) {
				slots[i] = new ItemStack(slots[i].getItem().setFull3D());
			}else{
				slots[i].stackSize--;
			}

			if(slots[i].stackSize <= 0) {
				slots[i] = null;
			}
		}
	}

}

public boolean hasPower() {
	return dualPower > 0;
}

public boolean isMashing () {
	return this.dualCookTime >0;
}

public void updateEntity() {
	boolean flag = this.hasPower();
	boolean flag1 = false;

	if(hasPower() && this.isMashing()) {
		this.dualPower--;
	}

	if(!worldObj.isRemote) {
		if (this.hasItemPower(this.slots[2]) && this.dualPower < (this.maxPower - this.getItemPower(this.slots[2]))) {
			this.dualPower += getItemPower(this.slots[2]);

			if(this.slots[2] != null) {
				flag1 = true;

				this.slots[2].stackSize--;

				if(this.slots[2].stackSize == 0) {
					this.slots[2] = this.slots[2].getItem().getContainerItem(this.slots[2]);
				}
			}
		}

		if (hasPower() && canMash()) {
			dualCookTime++;

			if (this.dualCookTime == this.mashingSpeed) {
				this.dualCookTime = 0;
				this.mashItem();
				flag1 = true;
			}
		}else{
			dualCookTime = 0;
		}

		if (flag != this.isMashing()) {
			flag1 = true;
			blockOven.updateBlockState(this.isMashing(), this.worldObj, this.xCoord, this.yCoord, this.zCoord);
		}
	}

	if (flag1) {
		this.markDirty();
	}


}


}

You should be really using @Override annotations.

 

About your problem:

You have to read the items from NBT in the same order in which they were saved.

You are saving two shorts and then tagList, so you have to read them in the same order.

You should be really using @Override annotations.

 

About your problem:

You have to read the items from NBT in the same order in which they were saved.

You are saving two shorts and then tagList, so you have to read them in the same order.

 

But how can i do this?(i am noob in coodin)

In your readFromNBT method you put: byte b0 = nbt1.getByte("slot")

and in your writeToNBT method you wrote: nbt1.setByte("Slot", (byte) i)

 

Which this in java is two separate strings, so when it reads it from the NBT its trying to find the byte with the name "slot" instead of "Slot"

You have to read the items from NBT in the same order in which they were saved.

You are saving two shorts and then tagList, so you have to read them in the same order.

False. You can write them in one order and read them in a totally different order, and it would still work.

Image NBT's like hashmaps. you give it the key and it gives u the value, no matter what u were reading before.

You have to read the items from NBT in the same order in which they were saved.

You are saving two shorts and then tagList, so you have to read them in the same order.

You are thinking of packets, in which the order most certainly does matter because it is a stream of bytes, but NBT, as others have pointed out, is key : value pairs, so order is irrelevant.