In this chapter, we learned a new way of looking at algorithms. The functional style of writing a program can simplify the analysis of its correctness, that is, you can easily understand why the program produces correct output. We saw a few patterns in functional programming, especially monads. We also saw how Java provides support for the functional style of programming through the syntax called lambda, which has existed from version 9 of Java. Finally, we saw how to use lambda effectively for functional programming.

Functional programs are, in general, easier to verify for correctness, but it is harder to compute their complexity. They generally perform either at the same speed as or slower than their imperative counterparts. It is a trade-off between development effort and computational efficiency. For smaller inputs, it is thus desirable to have a functional style of programming, whereas for processing large inputs, imperative style may be preferred.