static class AIHideInStone extends EntityAIWander
    {
        public boolean shouldExecute()
        {
            if (!this.silverfish.worldObj.getGameRules().getBoolean("mobGriefing"))
            {
                return false;
            }
            else if (this.silverfish.getAttackTarget() != null)
            {
                return false;
            }
            else if (!this.silverfish.getNavigator().noPath())
            {
                return false;
            }
            else //...
        }
    }