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[Solved] ItemStack amount is doubling randomly


onVoid
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Alright, so I have an item where when I break a block, the drop is changed based on a recipe system I have going.

The class where the recipes are added is here (yes I know it's ugly, I'll work on it):

	public static HashMap<String, ArrayList<Object>> blocks = new HashMap<String, ArrayList<Object>>();
	
	public static void addRecipe(String block, HashMap<Object, Integer> drops){
		ArrayList<Object> temp = new ArrayList<Object>();
		for (Object i : drops.keySet()){
			int x = drops.get(i);
			for (int y = 0; y < x; y++){
				temp.add(i);
			}
		}
		blocks.put(block, new ArrayList<Object>(temp));
		temp.clear();
		return;
	}
	
	public static void addRecipe(String block, Object drop){
		ArrayList<Object> temp = new ArrayList<Object>();
		temp.add(drop);
		blocks.put(block, new ArrayList<Object>(temp));
		temp.clear();
		return;
	}
	
	public static ArrayList<Object> getDrop(String block, EntityPlayer player){
		return blocks.get(block);
	}
	
	public static void init(){
		//LOG
		HashMap<Object, Integer> LOG = new HashMap<Object, Integer>();{
		LOG.put("block", 39);
		LOG.put(new ItemStack(Items.STICK), 45);
		LOG.put(new ItemStack(ItemsAdjunct.petrifiedWood, 1, 2), 8);
		LOG.put(new ItemStack(ItemsAdjunct.petrifiedWood, 1, 1), 4);
		LOG.put(new ItemStack(ItemsAdjunct.petrifiedWood, 1, 0), 4);
		}
		addRecipe("logWood", LOG);
		
		//LEAVES
		HashMap<Object, Integer> LEAVES = new HashMap<Object, Integer>();{
		LEAVES.put(null, 17);
		LEAVES.put(new ItemStack(ItemsAdjunct.leafDry, 1), 2);
		LEAVES.put(new ItemStack(ItemsAdjunct.leaf, 1), 1);
		}
		addRecipe("treeLeaves", LEAVES);
		
		addRecipe("dirt", new ItemStack(Blocks.GOLD_BLOCK, 1));
	}

The drop is calculated in the tool class, as a method ran from onBlockStartBreak, and that method is here:

	public static void calculateDrop(ItemStack itemstack, BlockPos pos, net.minecraft.entity.player.EntityPlayer player){
        IBlockState bs = player.getEntityWorld().getBlockState(pos);
        Block block = bs.getBlock();
        int[] blockIDs = OreDictionary.getOreIDs(new ItemStack(Item.getItemFromBlock(block), 1, block.damageDropped(bs)));
        ArrayList<String> blockNAMEs = new ArrayList<String>();
        for (int id : blockIDs){
        	blockNAMEs.add(OreDictionary.getOreName(id));
        }
        Random rand = new java.util.Random();
        ItemStack drop = ItemStack.EMPTY;
        	for (String name : blockNAMEs){
	            if (Pruner.blocks.keySet().contains(name)){
	            	player.getEntityWorld().setBlockToAir(pos);
	            	int outOf = Pruner.getDrop(name, player).size();
	            	Object j = Pruner.getDrop(name, player).get(rand.nextInt(outOf));
	            	if (j instanceof ItemStack){
	            		drop = (ItemStack)j;
		            	break;
	            	} else if (j instanceof String){
	            		if (((String)j).equals("block")){
	            			drop = new ItemStack (block.getItemDropped(bs, new Random(), block.damageDropped(bs)), 1, block.damageDropped(bs));
	    	            	break;
	            		}
	            	}
	            }
        	}
            //
            if (!drop.isEmpty()){
		        float f = 0.7F;
		        double d  = (double)(rand.nextFloat() * f) + (double)(1.0F - f) * 0.2D;
		        double d2 = (double)(rand.nextFloat() * f) + (double)(1.0F - f) * 0.2D;
		        net.minecraft.entity.item.EntityItem entityitem = new net.minecraft.entity.item.EntityItem(player.getEntityWorld(), (double)pos.getX() + d, (double)pos.getY(), (double)pos.getZ() + d2, drop);
		        entityitem.setDefaultPickupDelay();
		        player.getEntityWorld().spawnEntity(entityitem);
		        return;
            }
	}

Now, the issue I am having is that when I break the block that I am using to test (dirt block), at first I receive a single gold block like I am supposed to. But, as I keep breaking more, the amount that drops keeps doubling (I've done some bug testing, and it seems that the actual ItemStack inside of my blocks map is being edited. Now, the only time this map is mentioned in my mod (besides in contains, get, or keySet) is in the class I gave.

Also, init(), in the recipe class, is ran from my main class' FMLInitializationEvent only.

 

Help would be much appreciated, thanks.

Edited by onVoid
Solved
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In java everything that is an instance of Object is a reference-type. So, for example if you have this code

class Foo
{
	public int i = 0;
}

class Main
{
	static void main(string[] args)
	{
		Foo foo = new Foo();
		foo.i = 1;
		doStuff(foo);
		System.out.println(foo.i);
	}

	static void doStuff(Foo foo)
	{
		++foo.i;
	}
}

then the statement being printed into console will be 2. This is basic java.

So you have a Map<String, ItemStack[]>(your map is slightly different but effectively it's the same). Then in your drop class you get an ItemStack from said map and drop it to the player. Now the player has that ItemStack, but it is also still in your map. Thus every modification the player's inventory now does to that ItemStack is also applied to the one inside the map(because they are the same object). So if the player increases the stacksize of your itemstack by 1(say by picking it up) your map now contains the itemstack with the size of 2 and when it is dropped it will have a quantity of 2. Which when the player picks it up will become 4 and so on.

Basically use ItemStack#copy(or it may be called clone, don't remember and can't look it up rn) to create a copy of the itemstack in your map.

 

Unrelated issues:

Don't construct a new Random instance every time, there is no reason to do that.

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30 minutes ago, V0idWa1k3r said:

In java everything that is an instance of Object is a reference-type. So, for example if you have this code


class Foo
{
	public int i = 0;
}

class Main
{
	static void main(string[] args)
	{
		Foo foo = new Foo();
		foo.i = 1;
		doStuff(foo);
		System.out.println(foo.i);
	}

	static void doStuff(Foo foo)
	{
		++foo.i;
	}
}

then the statement being printed into console will be 2. This is basic java.

So you have a Map<String, ItemStack[]>(your map is slightly different but effectively it's the same). Then in your drop class you get an ItemStack from said map and drop it to the player. Now the player has that ItemStack, but it is also still in your map. Thus every modification the player's inventory now does to that ItemStack is also applied to the one inside the map(because they are the same object). So if the player increases the stacksize of your itemstack by 1(say by picking it up) your map now contains the itemstack with the size of 2 and when it is dropped it will have a quantity of 2. Which when the player picks it up will become 4 and so on.

Basically use ItemStack#copy(or it may be called clone, don't remember and can't look it up rn) to create a copy of the itemstack in your map.

 

Unrelated issues:

Don't construct a new Random instance every time, there is no reason to do that.

Thanks for the help, realizing that objects are universal is something that has tripped me up a few times in Java.

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