Get angle between two positions

Hello, I am making a plugin for electricity and I want to make realistic cables so I use an armor stand that has a chain in the head. I want that the head rotates at a specific angle between that two positions so the heads can form and straight line.

This is the code I have for now.

Code:

    public static void SpawnCable(Location from, Location to, Double space, Player p, ItemStack item)
    {
        from.setPitch(0);
        from.setYaw(0);

        to.setPitch(0);
        to.setYaw(0);

        World world = p.getWorld();

        double distance = from.distance(to);

        Vector p1 = from.toVector();
        Vector p2 = to.toVector();

        Vector vector = p2.clone().subtract(p1).normalize().multiply(space);

        double covered = 0;

        for (; covered < distance; p1.add(vector))
        {
            ArmorStand armorStand = (ArmorStand) world.spawnEntity(p1.toLocation(p.getWorld()), EntityType.ARMOR_STAND);

            armorStand.addEquipmentLock(EquipmentSlot.HEAD, ArmorStand.LockType.ADDING_OR_CHANGING);
            armorStand.addEquipmentLock(EquipmentSlot.CHEST, ArmorStand.LockType.ADDING_OR_CHANGING);
            armorStand.addEquipmentLock(EquipmentSlot.LEGS, ArmorStand.LockType.ADDING_OR_CHANGING);
            armorStand.addEquipmentLock(EquipmentSlot.FEET, ArmorStand.LockType.ADDING_OR_CHANGING);
            armorStand.addEquipmentLock(EquipmentSlot.HAND, ArmorStand.LockType.ADDING_OR_CHANGING);
            armorStand.addEquipmentLock(EquipmentSlot.OFF_HAND, ArmorStand.LockType.ADDING_OR_CHANGING);

            if(item.getItemMeta().getPersistentDataContainer().has(new NamespacedKey(BetterMC.plugin, "Color-Red"), PersistentDataType.STRING))
            {
                armorStand.setHelmet(CableColors.RED);
            }
            else if(item.getItemMeta().getPersistentDataContainer().has(new NamespacedKey(BetterMC.plugin, "Color-Black"), PersistentDataType.STRING))
            {
                armorStand.setHelmet(CableColors.BLACK);
            }
            else if(item.getItemMeta().getPersistentDataContainer().has(new NamespacedKey(BetterMC.plugin, "Color-Green"), PersistentDataType.STRING))
            {
                armorStand.setHelmet(CableColors.GREEN);
            }
            else if(item.getItemMeta().getPersistentDataContainer().has(new NamespacedKey(BetterMC.plugin, "Color-Blue"), PersistentDataType.STRING))
            {
                armorStand.setHelmet(CableColors.BLUE);
            }
            else if(item.getItemMeta().getPersistentDataContainer().has(new NamespacedKey(BetterMC.plugin, "Color-Pink"), PersistentDataType.STRING))
            {
                armorStand.setHelmet(CableColors.PINK);
            }
            else if(item.getItemMeta().getPersistentDataContainer().has(new NamespacedKey(BetterMC.plugin, "Color-Purple"), PersistentDataType.STRING))
            {
                armorStand.setHelmet(CableColors.PURPLE);
            }
            else if(item.getItemMeta().getPersistentDataContainer().has(new NamespacedKey(BetterMC.plugin, "Color-Yellow"), PersistentDataType.STRING))
            {
                armorStand.setHelmet(CableColors.YELLOW);
            }
            else if(item.getItemMeta().getPersistentDataContainer().has(new NamespacedKey(BetterMC.plugin, "Color-Brown"), PersistentDataType.STRING))
            {
                armorStand.setHelmet(CableColors.BROWN);
            }
            else if(item.getItemMeta().getPersistentDataContainer().has(new NamespacedKey(BetterMC.plugin, "Color-White"), PersistentDataType.STRING))
            {
                armorStand.setHelmet(CableColors.WHITE);
            }

            armorStand.setVisible(false);
            armorStand.setGravity(false);
            armorStand.setInvulnerable(true);
            armorStand.setSmall(true);
            armorStand.setBasePlate(false);

            Location armorstandLocation = armorStand.getLocation();

            Vector playerVec = to.toVector();
            Vector armorstandVec = armorstandLocation.toVector();

            Vector facingVector = playerVec.subtract(armorstandVec).normalize();

            armorstandLocation.setDirection(facingVector);
            armorStand.teleport(armorstandLocation);

            Vector inBetween = to.clone().subtract(armorstandLocation).toVector();
            Vector lookVec = armorstandLocation.getDirection();

            double angleDir = (Math.atan2(inBetween.getZ(),inBetween.getX()) / 2 / Math.PI * 360 + 360) % 360;
            double angleLook = (Math.atan2(lookVec.getZ(),lookVec.getX()) / 2 / Math.PI * 360 + 360) % 360;

            double angle = (angleDir - angleLook + 360) % 360;

            armorStand.setHeadPose(new EulerAngle(angle, 0, 0));

            covered += space;
        }
    }

If you need more info said me!

 

The problem is that the system of rotation doesn't work.