How do I get my Player to cast two fireballs at a time

I am making a upgrade menu and one of the upgrades is that it will allow my player to cast two fire balls, how do I get that to happen? I am using JavaScript. I have do it with C# before but it didnt work when I tried it with Java. The C# Script I have is:

else if (otherObject.tag == "BOC1" && Ammo > 0 && DoubleShot == 1) { StartCoroutine(DoubleShotAct1()); }

 IEnumerator DoubleShotAct()
 {
     Vector3 position = new Vector3(transform.position.x, transform.position.y + BulletOffset);
     Instantiate(Bullet, Barrel.transform.position, Quaternion.identity);
     yield return new WaitForSeconds (0.3f);
     Instantiate(Bullet, Barrel.transform.position, Quaternion.identity);
     Ammo --;
 }

How do I convert that into Java??