I was working on an bull entity that attacks an entity that attacked the bull, but the game crashes when I try to apply an AttributeModifier to reset the speed.

 

Error:

net.minecraft.util.ReportedException: Ticking entity
    at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:709) ~[MinecraftServer.class:?]
    at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:614) ~[MinecraftServer.class:?]
    at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:118) ~[IntegratedServer.class:?]
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:485) [MinecraftServer.class:?]
    at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:752) [MinecraftServer$2.class:?]
Caused by: java.util.ConcurrentModificationException
    at java.util.ArrayList$Itr.checkForComodification(Unknown Source) ~[?:1.8.0_131]
    at java.util.ArrayList$Itr.next(Unknown Source) ~[?:1.8.0_131]
    at net.minecraft.entity.ai.EntityAITasks.onUpdateTasks(EntityAITasks.java:70) ~[EntityAITasks.class:?]
    at net.minecraft.entity.EntityLiving.updateAITasks(EntityLiving.java:613) ~[EntityLiving.class:?]
    at net.minecraft.entity.EntityLivingBase.onLivingUpdate(EntityLivingBase.java:1983) ~[EntityLivingBase.class:?]
    at net.minecraft.entity.EntityLiving.onLivingUpdate(EntityLiving.java:431) ~[EntityLiving.class:?]
    at net.minecraft.entity.EntityAgeable.onLivingUpdate(EntityAgeable.java:138) ~[EntityAgeable.class:?]
    at net.minecraft.entity.passive.EntityAnimal.onLivingUpdate(EntityAnimal.java:56) ~[EntityAnimal.class:?]
    at net.minecraft.entity.EntityLivingBase.onUpdate(EntityLivingBase.java:1816) ~[EntityLivingBase.class:?]
    at net.minecraft.entity.EntityLiving.onUpdate(EntityLiving.java:250) ~[EntityLiving.class:?]
    at com.wotmod.mod.entity.BullEntity.onUpdate(BullEntity.java:111) ~[BullEntity.class:?]
    at net.minecraft.world.World.updateEntityWithOptionalForce(World.java:2298) ~[World.class:?]
    at net.minecraft.world.WorldServer.updateEntityWithOptionalForce(WorldServer.java:684) ~[WorldServer.class:?]
    at net.minecraft.world.World.updateEntity(World.java:2258) ~[World.class:?]
    at net.minecraft.world.World.updateEntities(World.java:2108) ~[World.class:?]
    at net.minecraft.world.WorldServer.updateEntities(WorldServer.java:515) ~[WorldServer.class:?]
    at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:703) ~[MinecraftServer.class:?]

public BullEntity(World p_i1683_1_) 
    {
        super(p_i1683_1_);
        clearTasks();
        this.tasks.addTask(1, new EntityAISwimming(this));
        this.tasks.addTask(2, new EntityAIMate(this, 1.0D));
        this.tasks.addTask(3, new EntityAITempt(this, 1.25D, Items.wheat, false));
        this.tasks.addTask(4, new EntityAIFollowParent(this, 1.25D));
        this.tasks.addTask(5, new EntityAIWander(this, 1.0D));
        this.tasks.addTask(6, new EntityAIWatchClosest(this, EntityPlayer.class, 6.0F));
        this.tasks.addTask(7, new EntityAILookIdle(this));
    }
    
    public void clearTasks() {
        this.tasks.taskEntries.clear();
        
    }

    @Override
    protected void applyEntityAttributes() {
        super.applyEntityAttributes();
        this.getAttributeMap().registerAttribute(SharedMonsterAttributes.attackDamage);
        this.getEntityAttribute(SharedMonsterAttributes.attackDamage).setBaseValue(6.0D);
    }
    
    @Override
    public boolean attackEntityFrom(final DamageSource p_70097_1_, float p_70097_2_) {
        if(p_70097_1_.getEntity() instanceof EntityLivingBase)
        {
           this.getEntityAttribute(SharedMonsterAttributes.movementSpeed).applyModifier(new AttributeModifier("speed", 0.299999997D, 0));
           this.tasks.addTask(0, new EntityAIAttackOnCollide(this, p_70097_1_.getEntity().getClass(), 1.0D, false));
           this.targetTasks.addTask(2, new EntityAINearestAttackableTarget(this, p_70097_1_.getEntity().getClass(), 0, true));
           final BullEntity b = this;
           Thread t = new Thread(){
             @Override
            public void run() {
                 super.run();
                while(true)
                {
                   
                    if(p_70097_1_.getEntity().isDead)
                    {
                        b.targetTasks.taskEntries.clear();
                        b.clearTasks();
                    }
                }
            }  
           };
           t.start();
           t.setName("Bull-Thread");
 
        }
        return super.attackEntityFrom(p_70097_1_, p_70097_2_);
    }
    
    @Override
    public void onUpdate() {
        
        if(this.targetTasks.taskEntries.size() == 0 && this.tasks.taskEntries.size() != 7)
        {
            this.getEntityAttribute(SharedMonsterAttributes.movementSpeed).applyModifier(new AttributeModifier("speed", - 0.299999997D, 0));
            this.tasks.addTask(1, new EntityAISwimming(this));
            this.tasks.addTask(2, new EntityAIMate(this, 1.0D));
            this.tasks.addTask(3, new EntityAITempt(this, 1.25D, Items.wheat, false));
            this.tasks.addTask(4, new EntityAIFollowParent(this, 1.25D));
            this.tasks.addTask(5, new EntityAIWander(this, 1.0D));
            this.tasks.addTask(6, new EntityAIWatchClosest(this, EntityPlayer.class, 6.0F));
            this.tasks.addTask(7, new EntityAILookIdle(this));
        }
        
        super.onUpdate();
    }
    
    @Override
    public boolean attackEntityAsMob(Entity p_70652_1_)
    {
        float f = (float)this.getEntityAttribute(SharedMonsterAttributes.attackDamage).getAttributeValue();
        int i = 0;

        if (p_70652_1_ instanceof EntityLivingBase)
        {
            f += EnchantmentHelper.getEnchantmentModifierLiving(this, (EntityLivingBase)p_70652_1_);
            i += EnchantmentHelper.getKnockbackModifier(this, (EntityLivingBase)p_70652_1_);
        }

        boolean flag = p_70652_1_.attackEntityFrom(DamageSource.causeMobDamage(this), f);

        if (flag)
        {
            if (i > 0)
            {
                p_70652_1_.addVelocity((double)(-MathHelper.sin(this.rotationYaw * (float)Math.PI / 180.0F) * (float)i * 0.5F), 0.1D, (double)(MathHelper.cos(this.rotationYaw * (float)Math.PI / 180.0F) * (float)i * 0.5F));
                this.motionX *= 0.6D;
                this.motionZ *= 0.6D;
            }

            int j = EnchantmentHelper.getFireAspectModifier(this);

            if (j > 0)
            {
                p_70652_1_.setFire(j * 4);
            }

            if (p_70652_1_ instanceof EntityLivingBase)
            {
                EnchantmentHelper.func_151384_a((EntityLivingBase)p_70652_1_, this);
            }

            EnchantmentHelper.func_151385_b(this, p_70652_1_);
        }

        return flag;
    }

 

Does it make any difference if I say that when I'm not resetting the speed it works just fine?

So, there is nothing I can do?

The code that created in order to attack except the new thread was from a tutorial.(I don't know forge and Minecraft code so well) 

Edited July 29, 20178 yr by WOTBLITZ

Wait, There one thing I can try. Fixing this :

• Most of Minecraft's code is not threadsafe, you cannot just spawn a 2nd thread and then start mocking around with game elements like entities inside it, you will get unspecified behavior at best and crashes at worse.

(thats the only thing I can change)

using onUpdate did fix it.