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Lambdas and Clean Code

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Lambdas and Clean Code

As with the introduction of any new tool, Java 8's lambda expressions have led to odd biases and poor use. Here are some considerations to keep your code clean.

· Java Zone
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As software developers, we behave like children. When we see shiny new things, we just have to play with them. That’s normal, accepted, and in general, even beneficial to our job… up to a point.

When Java started to provide annotations with version 5, there was a huge move toward using them. Anywhere. Everywhere. Even when it was not a good idea to do that. But it was new, hence it had to be good. Of course, when something is abused, there’s a strong movement against it — so that even when the usage of annotations may make sense, some developers might strongly be against it. There’s even a site about that (warning, trolling inside).

Unfortunately, we didn’t collectively learn from overusing annotations. With a lot of companies having migrated to Java 8, one starts to notice a lot of code making use of lambdas like this one:

List<Person> persons = ...;
persons.stream().filter(p -> {
    if (p.getGender() == Gender.MALE) {
        return true;
    }
    LocalDate now = LocalDate.now();
    Duration age = Duration.between(p.getBirthDate(), now);
    Duration adult = Duration.of(18, ChronoUnit.YEARS);
    if (age.compareTo(adult) > 0) {
        return true;
    }
    return false;
}).map(p -> p.getFirstName() + " " + p.getLastName())
  .collect(Collectors.toList());


This is just a stupid sample, but it gives a good feeling of the code I sometimes have to read. It’s, in general, longer and even more convoluted, or to be politically correct, it has room for improvement — a lot of room.

The first move would be to apply correct naming, as well as to move the logic to where it belongs to.

public class Person {

    // ...

    public boolean isMale() {
        return getGender() == Gender.MALE;
    }

    public boolean isAdult(LocalDate when) {
        Duration age = Duration.between(birthDate, when);
        Duration adult = Duration.of(18, ChronoUnit.YEARS);
        return age.compareTo(adult) > 0;
    }
}


This small refactoring already improves the readability of the lambda:

persons.stream().filter(p -> {
    if (p.isMale()) {
        return true;
    }
    LocalDate now = LocalDate.now();
    if (p.isAdult(now)) {
        return true;
    }
    return false;
}).map(p -> p.getFirstName() + " " + p.getLastName())
        .collect(Collectors.toList());


But it shouldn’t stop there. There’s an interesting bias regarding lambda: They have to be anonymous. Nearly all examples on the web show anonymous lambdas. But nothing could be further from the truth!

Let’s name our lambdas and check the results:

// Implementation details
Predicate<Person> isMaleOrAdult = p -> {
    if (p.isMale()) {
        return true;
    }
    LocalDate now = LocalDate.now();
    if (p.isAdult(now)) {
        return true;
    }
    return false;
};
Function<Person, String> concatenateFirstAndLastName = p -> p.getFirstName() + " " + p.getLastName();

// Core
persons.stream().filter(isMaleOrAdult).map(concatenateFirstAndLastName)


Nothing mind-blowing. Yet, notice that the stream itself (the last line) has become more readable, not hidden behind implementation details. It doesn’t prevent developers from reading them, but only if necessary.

Tools are tools. Lambdas are just one of them in a Java developer’s toolbelt. But concepts are forever.

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Topics:
java ,lambda expressions ,clean code ,refactoring ,tutorial

Published at DZone with permission of Nicolas Frankel, DZone MVB. See the original article here.

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