Getting Amount Of A Certain Item In Inventory?

Looking at the API there are two ways to create an Item which is required by

client.getInventory().getAmount(Item);

Which is

Item = new Item(); // Fake ConstructorItem = new Item(itemID, itemAmmount);

Now, if I knew the exact amount of the item i needed to create this would not be a problem, although this is what the original function

client.getInventory().getAmount(Item);

would be for, is it not? Perhaps I'm missing something, I'm just trying to see how many runes i have left in my inventory. :facedesk: