Add concept: `Functional Programming`

After doing aprox 40+ exercises on the Java learning path on exercism, I thought the addition of this concept could be very valuable, there is a lot of usage in the `Dig Deeper` and as well in the community solutions about `Functional Programming`.
But not probably all the users are familiar with it. Maybe the concept could be separated on smaller topics like `Functions`, `Consumers`, `Predicates`, `Supliers`, `Streams` and `Lambdas` .

Maybe some of the exercise of this topic could be like transforming a for loop into using functional programming, or something like that.

What are the thoughts on this one?