This code makes it so that when a bat is killed it drops a Bat Soul but what I need is for that to only happen IF you kill it using a certain sword, does anyone know how I would do that?:

 

//Bat Soul
@SubscribeEvent
public void addEntityDrop1 (LivingDropsEvent event) {
	if (event.entity instanceof EntityBat) {
		ItemStack itemstack = new ItemStack(MASouls.BatSoul, 1);
		event.drops.add(new EntityItem(event.entity.worldObj, event.entity.posX, event.entity.posY, event.entity.posZ, itemstack));
	}
}

Make sure to check null.  Not all DamageSources have a source entity.

Okay thanks guys and how would I make it so the soul has a chance to drop from 10% - 90%?

10% - 90% that means one value ranging from 10% up to 90% but only one a ta time

No I mean up to 90% as in a single value of either 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%

Do you even probability?

 

You either have 10% (1/10 of drops will be soul) chance of dropping item or 90% (almost always, 9/10, there will be soul), you can't have from-to.

 

 

That's not what I'm saying... I'm saying ONE VALUE as in on percentage not a range of just 10% or 20% or 30% etc not 20%, 21%, 22%, 23% just 20% OR 30%

Two random numbers like that would result in less than a 50% I think, but I'm not in a place to so the math.

 

However, that two-numbers thing does get you a different result if you are returning a float (as compared to a uniform random), the Wald Distribution (Inverse Gaussian) uses that method.