TIMTOWTDI and Java

(and not only Java!)

Grzegorz Rożniecki (@xaerxess)

About me

Java / Perl / JavaScript developer

Software reader / writer

xaerxess.pl

@xaerxess

Xaerxess

About this talk

Slides | Source on GitHub

This work is licensed under a Creative Commons Attribution 4.0 International License.

TIMTOWTDI

There is more than one way to do it

Tim Toady

"The very fact that it's possible to write messy programs in Perl is also what makes it possible to write programs that are cleaner in Perl than they could ever be in a language that attempts to enforce cleanliness. The potential for greater good goes right along with the potential for greater evil."

Why?

Python Zen

There should be one
- and preferably only one -
obvious way to do it

Tim Toady in practice

Tim Toady in practice

"There are only two kinds of languages: the ones people complain about and the ones nobody uses"

"There are only 10 kinds of languages: the ones people complain about and the ones nobody uses"

Perl doing for loop

for (my $i = 0; $i <= 3; ++$i) {
    print $i;
}
            

Perl doing for loop

for my $i (0..3) {
    print $i;
}
            

Perl doing for loop

for (0..3) {
    print $_;
}
            

Perl doing for loop

for (0..3) {
    print;
}
            

Perl doing for loop

print for (0..3);
            

Linguistic relativity

vs

Universal grammar

Sapir–Whorf hypothesis

Edward Sapir	Benjamin Whorf
linguistics theory	Hopi - time & space

TIMTOWTDI

BSCINABTE

There’s more than one way to do it
but sometimes consistency is not a bad thing either

OOP in Perl

package Foo;

sub new {
  my $class = shift;
  my $self = { }; # or [ ] or any arbitrary scalar value
  return bless $self, $class;
}

1;
            

Standards

People like rules and guidelines. They like to agree with them, or to argue with them.

Inconsistency

TIMTOWTDI?

Java syntax

final class Person {

  private final String name;
  private final Integer age;

  public Person(String name, Integer age) {
    this.name = name;
    this.age = age;
  }

  public String getName() {
    return name;
  }

  public Integer getAge() {
    return age;
  }

  @Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((age == null) ? 0 : age.hashCode());
    result = prime * result + ((name == null) ? 0 : name.hashCode());
    return result;
  }

  @Override
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (obj == null)
      return false;
    if (getClass() != obj.getClass())
      return false;
    Person other = (Person) obj;
    if (age == null) {
      if (other.age != null)
        return false;
    } else if (!age.equals(other.age))
      return false;
    if (name == null) {
      if (other.name != null)
        return false;
    } else if (!name.equals(other.name))
      return false;
    return true;
  }

  @Override
  public String toString() {
    return "Person [name=" + name + ", age=" + age + "]";
  }

}
            

case class Person(name: String, age: Int)
            

Java 7+: Objects
Java < 7 - Guava: Objects

  @Override
  public int hashCode() {
    return Objects.hash(name, age);
  }

  @Override
  public boolean equals(final Object obj) {
    if (!(obj instanceof Person))
      return false;
    final Person other = (Person) obj;
    return Objects.equals(this.name, other.name)
        && Objects.equals(this.age, other.age);
  }
            

Better?

Guava 18+: MoreObjects.toStringHelper
Guava < 18: Objects.toStringHelper

  @Override
  public String toString() {
    return MoreObjects.toStringHelper(this)
        .add("name", name)
        .add("age", age)
        .toString();
  }
            

Also better?

  @Override
  public String toString() {
    return "Person [name=" + name + ", age=" + age + "]";
  }
            

Lombok: @Value

@Value public class Person {
  String name;
  Integer age;
}
            

Lombok: black magic

Google AutoValue: @AutoValue

@AutoValue
abstract class Person {

  public static Person create(String name, Integer age) {
    return new AutoValue_Person(name, age);
  }

  public abstract String getName();
  public abstract int getAge();
}
            

Good trade-off?

Legacy

So, why would you ever use object arrays?

• have to interact with an API that uses them, and you can't fix that API
• convert to/from a List as close to that API as you can
• have a reliable benchmark that shows you're actually getting better performance with them
• benchmarks can lie, and often do
• can't think of any other reasons

JVM languages

• JVM is great!
• Scala, Clojure, Jython, JRuby
• ...but employers don't trust them...
• ...and there's big need for Java devs, not JVM-based devs
• :-(

Coding standards

• Google Java code conventions
• Sun Oracle Java code conventions

Ex. consistent IDE preferences

The "final" battle

Best practices

Lambdas

"Closures feel to me like one of these design Black Holes. (...) So, should we just give in to the force of gravity and go the rest of the way? The debate's afoot. It's going to be an entertaining year."

"Java has closures, it's just called 'anonymous inner classes' (...). [They] are the better and more 'java-way' to do closures. Adding an additional syntax for closures will only make the language more complex without solving even one real problem."

...and in 2014 (finally) instead of this:

List<Album> favs = new ArrayList<>();
for (Album a : albums) {
    boolean hasFavorite = false;
    for (Track t : a.tracks) {
        if (t.rating >= 4) {
            hasFavorite = true;
            break;
        }
    }
    if (hasFavorite) {
        favs.add(a);
    }
}
Collections.sort(favs, new Comparator<Album>() {
    @Override public int compare(Album a1, Album a2) {
        return a1.name.compareTo(a2.name);
}});
            

...you can do this:

List<Album> sortedFavs =
  albums.stream()
        .filter(a -> a.tracks.anyMatch(t -> (t.rating >= 4)))
        .sorted(Comparator.comparing(a -> a.name))
        .collect(Collectors.toList());
            

There is more than one way to do it, finally!