ArrayIndexOutOfBoundsException

So today I wanted to write a "simple" shop plugin but I ran into this hell of an exception and I don't know how to fix it.

The line in question is:

Code (Text):

if (item_names.get(i).contains("/")) {

The sorrounding code is following:

Code (Text):

for (int i = 0; i < ItemManager.items.get(name).size(); i++) {
            if (item_names.get(i).contains("/")) {
            String[] split = item_names.get(i).split("/");
            String[] split2 = items_pre.get(item_names.get(i)).split("/");
                List<String> test = new ArrayList<String>();

                test.add("§7§lPreis: §c" + split2[0]);
                test.add("§7§lVerkaufen fuer: §c" + split2[1]);

                ItemStack item = new ItemStack(Material.valueOf(split[0]), 1, Short.valueOf(split[1]));
                ItemMeta item_m = item.getItemMeta();
                item_m.setLore(test);
                item.setItemMeta(item_m);

                inv.setItem(i, item);

To explain this - so you can better undstand what I'm trying to do.

I have an ItemManager which has a few lists in it (including item_names (ArrayList) and items_pre (HashMap))
Every entry in item_names is just the name of the variable of the item in Material#
Example: Entry in my list: IRON_INGOT
Result in Material#: Material.IRON_INGOT
items_pre are just the Items with the buy / sell values and metadatas as well as the Material# variable
attached.
Example: Entry in my list: Key: STONE/1 <- the 1 being the metadata (in this case granite)
Variable: 25(buy value)/15(sell value)
In this case the list item_names has 17 Entrys.

The Exception is following:

Code (Text):

Caused by: java.lang.IndexOutOfBoundsException: Index: 17, Size: 17
        at java.util.ArrayList.rangeCheck(ArrayList.java:657) ~[?:1.8.0_201]
        at java.util.ArrayList.get(ArrayList.java:433) ~[?:1.8.0_201]
        at me.blubo.development.events.InventoryClickEventHandler.prepareInv(InventoryClickEventHandler.java:121) ~[?:?]
        at me.blubo.development.events.InventoryClickEventHandler.onClick(InventoryClickEventHandler.java:86) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_201]
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_201]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_201]
        at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_201]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
        ... 15 more

If any questions about my code remain - please feel free to ask.
Thanks for reading and I hope you can help me.

 

They are not the same lists but they do have the excact same amount of entries within them (because I manually entry them into said lists)