Error with custom creative tab sorting

[Malkierian]

So, before anyone says anything, yes, I followed this tutorial:

However, when I set up the tabSorter, looking like this:

tabSorter = Ordering.explicit(order).onResultOf(new Function<ItemStack, Item>() {

I get this error:

The method onResultOf(Function<F,? extends Item>) in the type Ordering<Item> is not applicable for the arguments (new Function<ItemStack,Item>(){})

And I can't figure out why.  I followed the tutorial exactly.  I'm in Eclipse, and I think I have Java 1.6 as my compatibility and runtime environment, but I tried 1.7 and 1.8 and there wasn't a difference.  Any ideas?

[Choonster]

The Ordering class is from the Guava library, which uses its own functional interfaces (that predate Java 8). Make sure you've imported com.google.common.base.Function (Guava) rather than java.util.function.Function (Java 8).

[Malkierian]

Gah, I didn't even think about checking the imports....   Thanks.