java8 experiment - normandy jug
TRANSCRIPT
Java 8 eXperiment(s)François SarradinNormandy JUG20 octobre 2015
WARNING!!!
françois sarradin• ippon technologies (ippon.fr)
• manager technique capitalisation
• extremist programmer, FP, agilité
• http://brownbaglunch.fr/
• twitter: @fsarradin
• blog: https://kerflyn.wordpress.com/
plan
1. héritage multiple
2. exception
3. pattern matching
et du live coding !!!
héritage multiple
objet = état + comportement
en java 8, on peut faire de l’héritage multiple de comportement
mais peut-on faire de l’héritage multiple d’état ?
un mail de Brian GoetzSubject: Re: From virtual extension methods to mixingFrom: Brian Goetz <…@oracle.com>Date: Mon, 9 Jul 2012 07:50:11 -0400Cc: [email protected]: François Sarradin <…@gmail.com>
Please don't encourage techniques like this. There are a zillion "clever" things you can do in Java, but shouldn't. We knew it wouldn’t be long before someone suggested this, and we can't stop you. But please, use your power for good, and not for evil. Teach people to do it right, not to abuse it.
But please, use your power for good, and not for evil.
Please don't encourage techniques like this.
un autre mail de Brian GoetzSubject: Re: From virtual extension methods to mixinsFrom: Brian Goetz <…@oracle.com>Date: Tue, 10 Jul 2012 19:51:55 -0400To: François Sarradin <…@gmail.com>
[…]
The bottom line is:
interfaces cannot be counted on to have identity.
Which is a good thing, but can bite the "clever" from behind :)
ce qu’il faut retenir
un mail de Brian GoetzSubject: Re: From virtual extension methods to mixingFrom: Brian Goetz <…@oracle.com>Date: Mon, 9 Jul 2012 07:50:11 -0400Cc: [email protected]: François Sarradin <…@gmail.com>
Please don't encourage techniques like this. There are a zillion "clever" things you can do in Java, but shouldn't. We knew it wouldn’t be long before someone suggested this, and we can't stop you. But please, use your power for good, and not for evil. Teach people to do it right, not to abuse it.
There are a zillion "clever" things you can do in Java, but
shouldn't.
exception
sun.misc.Unsafe est voué à disparaître ?
checked exception non déclarée
Field f = Unsafe.class.getDeclaredField("theUnsafe");f.setAccessible(true);Unsafe unsafe = (Unsafe) f.get(null);
// throw undeclared checked exceptionunsafe.throwException(new IOException());
alternative ?
ce qu’il faut retenir
limiter le nombre de sous-classes
public class Base { private Base() {}
public static class Class1 extends Base {} public static class Class2 extends Base {} // ...}
type checking
• limitation des sous-classes + generics => TDD
• TDD = type driven development
• ATTENTION !!! null interdit (checkstyle)
pyramide de test
UI
Intégration
Unitaire
Compilateur
pattern matching
Java 8 introduit la programmation fonctionnelle
peut-on tenter d’y introduire le pattern matching
pattern matching (scala)
myValue match { case "hello" => println("hello world") case i: Int => println("int: $i") case Add(a, b) => println("$a + $b = ${a + b}") case _ => println("what else!")}
ce qu’il faut retenir
dsl en javaFirstWord firstWord(T t) { return new FirstWord(t); }
class FirstWord { final T t; FirstWord(T t) { this.t = t; }
FirstWord repeat(T t0) { return new FirstWord(t + t0); } SecondWord secondWord(R r) { return new SecondWord(r); }
class SecondWord(R r) { final R r; SecondWord(R r) { this.r = r; }
S end() { return /* ... */; } }}
functional apis (beyond java 8)• fugue (https://bitbucket.org/atlassian/fugue)
• functional java (http://www.functionaljava.org/)
• totallylazy (http://totallylazy.com/)
• jOOλ (https://github.com/jOOQ/jOOL)
• javaslang (http://javaslang.com/)
• cyclops (https://github.com/aol/cyclops)
conclusion
• optimisation en java (ne pas trop avec les concepts)
• limiter le nombres de sous-classes
• type driven development
• dsl en java
KEEPCALMAND
THANKYOU