I am wanting to make my mob at a distance of up to 6 blocks attack colliding with the player and starting from 6 blocks begin to Wither Skulls attack, but I can not, but I don't know and need help of you...

 

My Grim Reaper Entity Class:

 

package mike.bathicraft.mob;

import mike.bathicraft.items.GerenciadorDeItems;
import mike.bathicraft.lib.Strings;
import net.minecraft.block.Block;
import net.minecraft.entity.Entity;
import net.minecraft.entity.EntityAgeable;
import net.minecraft.entity.SharedMonsterAttributes;
import net.minecraft.entity.ai.EntityAIAttackOnCollide;
import net.minecraft.entity.ai.EntityAIBase;
import net.minecraft.entity.ai.EntityAIHurtByTarget;
import net.minecraft.entity.ai.EntityAINearestAttackableTarget;
import net.minecraft.entity.ai.EntityAISwimming;
import net.minecraft.entity.ai.EntityAIWander;
import net.minecraft.entity.ai.EntityAIWatchClosest;
import net.minecraft.entity.boss.BossStatus;
import net.minecraft.entity.boss.IBossDisplayData;
import net.minecraft.entity.monster.EntityMob;
import net.minecraft.entity.passive.EntityAnimal;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.entity.projectile.EntityLargeFireball;
import net.minecraft.entity.projectile.EntityWitherSkull;
import net.minecraft.init.Items;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.util.MathHelper;
import net.minecraft.util.Vec3;
import net.minecraft.world.World;

public class EntityCeifador extends EntityMob implements IBossDisplayData{

 private EntityAIAttackOnCollide aiAttackOnCollide = new EntityAIAttackOnCollide(this, EntityPlayer.class, 1.0F, true);

public EntityCeifador(World world) {
	super(world);
	isImmuneToFire = true;
	this.setSize(0.9F, 1.9F);

}

   @Override
    protected void applyEntityAttributes()
    {
        
        super.applyEntityAttributes();
        this.getEntityAttribute(SharedMonsterAttributes.attackDamage).setBaseValue(26.0D);
        this.getEntityAttribute(SharedMonsterAttributes.followRange).setBaseValue(40.0D);
        this.getEntityAttribute(SharedMonsterAttributes.movementSpeed).setBaseValue(0.45D);
        this.getEntityAttribute(SharedMonsterAttributes.maxHealth).setBaseValue(2000.0D);
        
    }
   
   public void onLivingUpdate()
   {
	   super.onLivingUpdate();
   BossStatus.setBossStatus(this, true);
   }		

	protected Item getDropItem(){
		return GerenciadorDeItems.EssenciaDaMorte;
	}

	protected void dropRareDrop(int par1){
		switch (this.rand.nextInt(3)){

		case 0:
			this.dropItem(GerenciadorDeItems.EssenciaDaMorte, 12);

		}
	}

	 protected String getLivingSound()
	    {
	        return "bathicraft:";
	    }

	   
	    protected String getHurtSound()
	    {
	        return "bathicraft:";
	    }

	  
	    protected String getDeathSound()
	    {
	        return "bathicraft:";
	    }
	    
	      protected void playStepSound(int par1, int par2, int par3, int par4)
	        {
	                this.worldObj.playSoundAtEntity(this, null, 0.15F,  1.0F);
	        }
	      
	      public ItemStack getHeldItem()
			 {
			 return heldItem;
			 }

			 private static final ItemStack heldItem = new ItemStack(GerenciadorDeItems.Gadanha, 1);

			    @Override
		        public void attackEntity(Entity entity, float arg1) {
		               
		                this.arrowHitTimer++;
		               
		                if (this.arrowHitTimer == 20)
		        {
		                       
		                        if(entity instanceof EntityPlayer) {
		                                Vec3 look = this.getLookVec();
		                               
		                                EntityWitherSkull var3 = new EntityWitherSkull(this.worldObj, this, 1, 1, 1);
		                                var3.setPosition(this.posX + look.xCoord * 1, this.posY + look.yCoord * 1, this.posZ + look.zCoord * 1);
		                                var3.accelerationX = look.xCoord * 0.1;
		                                var3.accelerationY = look.yCoord * 0.1;
		                                var3.accelerationZ = look.zCoord * 0.1;
		                        this.worldObj.spawnEntityInWorld(var3);
		                        this.arrowHitTimer = -40;
		                        	}
		        }else {
		        }
		        }
	    
}

Look Skeleton.

Look Skeleton.

 

I've been looking, I saw some things up, but to add to my mob, nothing happened...

please help me, I need to finish is part of programming to continue my mod