Over a million developers have joined DZone.

Functional Programming in Java – Venkat Subramaniam: Book Review

· DevOps Zone

Discover how to optimize your DevOps workflows with our cloud-based automated testing infrastructure, brought to you in partnership with Sauce Labs

I picked up Venkat Subramaniam’s ‘Functional Programming in Java: Harnessing the Power of Java 8 Lambda Expressions‘ to learn a little bit more about Java 8 having struggled to find any online tutorials which did that.

A big chunk of the book focuses on lambdas, functional collection parameters and lazy evaluation which will be familiar to users of C#, Clojure, Scala, Haskell, Ruby, Python, F# or libraries like totallylazy and Guava.

Although I was able to race through the book quite quickly it was still interesting to see how Java 8 is going to reduce the amount of code we need to write to do simple operations on collections.

I wrote up my thoughts on lambda expressions instead of auto closeable, using group by on collections andsorting values in collections in previous blog posts.

I noticed a couple of subtle differences in the method names added to collection e.g. skip/limit are there instead of take/drop for grabbing a subset of said collection.

There are also methods such as ‘mapToInt’ and ‘mapToDouble’ where in other languages you’d just have a single ‘map’ and it would handle everything.

Over the last couple of years I’ve used totallylazy on Java projects to deal with collections and while I like the style of code it encourages you end up with a lot of code due to all the anonymous classes you have to create.

In Java 8 lambdas are a first class concept which should make using totallylazy even better.

In a previous blog post I showed how you’d go about sorted a collection of people by age. In Java 8 it would look like this:

List<Person> people = Arrays.asList(new Person("Paul", 24), new Person("Mark", 30), new Person("Will", 28));
people.stream().sorted(comparing(p -> p.getAge())).forEach(System.out::println)

I find the ‘comparing’ function that we have to use a bit unintuitive and this is what we’d have using totallylazy pre Java 8:

Sequence<Person> people = sequence(new Person("Paul", 24), new Person("Mark", 30), new Person("Will", 28));
people.sortBy(new Callable1<Person, Integer>() {
    public Integer call(Person person) throws Exception {
        return person.getAge();

Using Java 8 lambdas the code is much simplified:

Sequence<Person> people = sequence(new Person("Paul", 24), new Person("Mark", 30), new Person("Will", 28));

If we use ‘forEach’ to print out each person individually we end up with the following:

Sequence<Person> people = sequence(new Person("Paul", 24), new Person("Mark", 30), new Person("Will", 28));
people.sortBy(Person::getAge).forEach((Consumer<? super Person>) System.out::println);

The compiler can’t work out whether we want to use the forEach method from totallylazy or from Iterable so we end up having to cast which is a bit nasty.

I haven’t yet tried converting the totallylazy code I’ve written but my thinking is that the real win of Java 8 will be making it easier to use libraries like totallylazy and Guava.

Overall the book describes Java 8′s features very well but if you’ve used any of the languages I mentioned at the top it will all be very familiar – finally Java has caught up with the rest!

Download “The DevOps Journey - From Waterfall to Continuous Delivery” to learn learn about the importance of integrating automated testing into the DevOps workflow, brought to you in partnership with Sauce Labs.


Published at DZone with permission of Mark Needham, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

The best of DZone straight to your inbox.

Please provide a valid email address.

Thanks for subscribing!

Awesome! Check your inbox to verify your email so you can start receiving the latest in tech news and resources.

{{ parent.title || parent.header.title}}

{{ parent.tldr }}

{{ parent.urlSource.name }}