I want my mob to have a ranged attack and then it will have a cooldown and during the cooldown I want the champion to do melee attacks, I did the Iprojectile and I tried adding both tasks to see if it will just do it but it starts melee one spawned and then it decides to go ranged and stay ranged.

 

package leagueofcrafters.entity;

import leagueofcrafters.entity.projectiles.EntityPukeball;
import net.minecraft.entity.Entity;
import net.minecraft.entity.EntityLivingBase;
import net.minecraft.entity.IRangedAttackMob;
import net.minecraft.entity.SharedMonsterAttributes;
import net.minecraft.entity.ai.EntityAIArrowAttack;
import net.minecraft.entity.ai.EntityAIAttackOnCollide;
import net.minecraft.entity.ai.EntityAIBreakDoor;
import net.minecraft.entity.ai.EntityAIHurtByTarget;
import net.minecraft.entity.ai.EntityAILookIdle;
import net.minecraft.entity.ai.EntityAIMoveThroughVillage;
import net.minecraft.entity.ai.EntityAIMoveTowardsRestriction;
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.monster.EntityMob;
import net.minecraft.entity.passive.EntityVillager;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.util.MathHelper;
import net.minecraft.world.World;

public class EntityNuNu extends EntityMob implements IRangedAttackMob {

private static int timer;

public EntityNuNu(World par1World) {
	super(par1World);
	this.tasks.addTask(0, new EntityAISwimming(this));
	this.tasks.addTask(1, new EntityAIBreakDoor(this));
	this.tasks.addTask(2, new EntityAIAttackOnCollide(this, EntityPlayer.class, 1.0D, false));
	this.tasks.addTask(3, new EntityAIAttackOnCollide(this, EntityVillager.class, 1.0D, true));
	this.tasks.addTask(4, new EntityAIMoveTowardsRestriction(this, 1.0D));
	this.tasks.addTask(5, new EntityAIMoveThroughVillage(this, 1.0D, false));
	this.tasks.addTask(6, new EntityAIWander(this, 1.0D));
	this.tasks.addTask(7, new EntityAIWatchClosest(this, EntityPlayer.class, 8.0F));
	this.tasks.addTask(7, new EntityAILookIdle(this));
	this.tasks.addTask(2, new EntityAIArrowAttack(this, 1.0D, 60, 10.0F));
	this.targetTasks.addTask(1, new EntityAIHurtByTarget(this, true));
	this.targetTasks.addTask(2, new EntityAINearestAttackableTarget(this, EntityPlayer.class, 0, true));
	this.targetTasks.addTask(2, new EntityAINearestAttackableTarget(this, EntityVillager.class, 0, false));

}

@Override
public boolean isAIEnabled() {
	return true;
}

@Override
protected Entity findPlayerToAttack() {
	double d0 = 16.0D;
	return this.worldObj.getClosestVulnerablePlayerToEntity(this, d0);
}

@Override
public void onLivingUpdate() {
	if (!this.worldObj.isRemote && this.timer > 0) {
		timer--;
	}
	super.onLivingUpdate();
}

@Override
protected void applyEntityAttributes() {
	super.applyEntityAttributes();
	this.getEntityAttribute(SharedMonsterAttributes.movementSpeed).setAttribute(0.2D);
}

@Override
public void attackEntityWithRangedAttack(EntityLivingBase entitylivingbase, float f) {
	if (timer == 0) {
		EntityPukeball entityPukeball = new EntityPukeball(this.worldObj, this);
		double d0 = entitylivingbase.posX - this.posX;
		double d1 = entitylivingbase.posY + (double) entitylivingbase.getEyeHeight() - entityPukeball.posY - 2;
		double d2 = entitylivingbase.posZ - this.posZ;
		float f1 = MathHelper.sqrt_double(d0 * d0 + d2 * d2) * 0.2F;
		entityPukeball.setThrowableHeading(d0, d1 + (double) f1, d2, 1.6F, 12.0F);
		this.worldObj.spawnEntityInWorld(entityPukeball);
		timer = 250;

	} else {
		this.targetTasks.addTask(4, new EntityAINearestAttackableTarget(this, EntityPlayer.class, 0, true));
		 this.attackEntity(entitylivingbase, f);
		 this.attackEntityAsMob(entitylivingbase);
	}
}

protected void attackEntity(Entity par1Entity, float par2) {
	float f1 = this.getBrightness(1.0F);

	if (f1 > 0.5F && this.rand.nextInt(100) == 0) {
		this.entityToAttack = null;
	} else {
		if (par2 > 2.0F && par2 < 6.0F && this.rand.nextInt(10) == 0) {
			if (this.onGround) {
				double d0 = par1Entity.posX - this.posX;
				double d1 = par1Entity.posZ - this.posZ;
				float f2 = MathHelper.sqrt_double(d0 * d0 + d1 * d1);
				this.motionX = d0 / (double) f2 * 0.5D * 0.800000011920929D + this.motionX * 0.20000000298023224D;
				this.motionZ = d1 / (double) f2 * 0.5D * 0.800000011920929D + this.motionZ * 0.20000000298023224D;
				this.motionY = 0.4000000059604645D;
			}
		} else {
			super.attackEntity(par1Entity, par2);
		}
	}
}
}

I have not attempted doing what your trying before, but i know you can add and remove tasks at any point in the Entities code. so you could remove the EntityAIArrowAttack task when it shoots and arrow, then after the cooldown readd it.

private static int timer;

static is probably not good.