Deep Dive Kotlin :
du Hello World au ByteCode

Speakers

Emmanuel Vinas

Expert Android & Java @emmanuelvinas emmanuel@monkeypatch.io

Igor Laborie

Expert Java & Web @ilaborie igor@monkeypatch.io

🗺 Roadmap

ByteCode Java ?
Introduction Kotlin
Les bases
null-safety
Les types
Les fonctions
Les lambdas
Les classes
Pause
ByteCode Android
Autres structures
Extensions de fonctions
Les collections
Les delegates
Un peu plus sur les fonctions
Conclusion

ByteCode Java ?

javac

HelloWorld.java

package _00_helloworld;

public class HelloWorld {

    public static void main(String[] args) {
        System.out.println("Hello Devoxx");
    }
}

javac HelloWorld.java

Java ByteCode binary

hexdump -C HelloWorld.class

00000000  ca fe ba be 00 00 00 34  00 1d 0a 00 06 00 0f 09  |.......4........|
00000010  00 10 00 11 08 00 12 0a  00 13 00 14 07 00 15 07  |................|
00000020  00 16 01 00 06 3c 69 6e  69 74 3e 01 00 03 28 29  |........()|
00000030  56 01 00 04 43 6f 64 65  01 00 0f 4c 69 6e 65 4e  |V...Code...LineN|
00000040  75 6d 62 65 72 54 61 62  6c 65 01 00 04 6d 61 69  |umberTable...mai|
00000050  6e 01 00 16 28 5b 4c 6a  61 76 61 2f 6c 61 6e 67  |n...([Ljava/lang|
00000060  2f 53 74 72 69 6e 67 3b  29 56 01 00 0a 53 6f 75  |/String;)V...Sou|
00000070  72 63 65 46 69 6c 65 01  00 0f 48 65 6c 6c 6f 57  |rceFile...HelloW|
00000080  6f 72 6c 64 2e 6a 61 76  61 0c 00 07 00 08 07 00  |orld.java.......|
00000090  17 0c 00 18 00 19 01 00  0c 48 65 6c 6c 6f 20 44  |.........Hello D|
000000a0  65 76 6f 78 78 07 00 1a  0c 00 1b 00 1c 01 00 19  |evoxx...........|
000000b0  5f 30 30 5f 68 65 6c 6c  6f 77 6f 72 6c 64 2f 48  |_00_helloworld/H|
000000c0  65 6c 6c 6f 57 6f 72 6c  64 01 00 10 6a 61 76 61  |elloWorld...java|
000000d0  2f 6c 61 6e 67 2f 4f 62  6a 65 63 74 01 00 10 6a  |/lang/Object...j|
000000e0  61 76 61 2f 6c 61 6e 67  2f 53 79 73 74 65 6d 01  |ava/lang/System.|
000000f0  00 03 6f 75 74 01 00 15  4c 6a 61 76 61 2f 69 6f  |..out...Ljava/io|
00000100  2f 50 72 69 6e 74 53 74  72 65 61 6d 3b 01 00 13  |/PrintStream;...|
00000110  6a 61 76 61 2f 69 6f 2f  50 72 69 6e 74 53 74 72  |java/io/PrintStr|
00000120  65 61 6d 01 00 07 70 72  69 6e 74 6c 6e 01 00 15  |eam...println...|
00000130  28 4c 6a 61 76 61 2f 6c  61 6e 67 2f 53 74 72 69  |(Ljava/lang/Stri|
00000140  6e 67 3b 29 56 00 21 00  05 00 06 00 00 00 00 00  |ng;)V.!.........|
00000150  02 00 01 00 07 00 08 00  01 00 09 00 00 00 1d 00  |................|
00000160  01 00 01 00 00 00 05 2a  b7 00 01 b1 00 00 00 01  |.......*........|
00000170  00 0a 00 00 00 06 00 01  00 00 00 03 00 09 00 0b  |................|
00000180  00 0c 00 01 00 09 00 00  00 25 00 02 00 01 00 00  |.........%......|
00000190  00 09 b2 00 02 12 03 b6  00 04 b1 00 00 00 01 00  |................|
000001a0  0a 00 00 00 0a 00 02 00  00 00 06 00 08 00 07 00  |................|
000001b0  01 00 0d 00 00 00 02 00  0e                       |.........|
000001b9

Explorons le ByteCode

javap -c HelloWorld.class

Compiled from "HelloWorld.java"
public class _00_helloworld.HelloWorld {
  public _00_helloworld.HelloWorld();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return

  public static void main(java.lang.String[]);
    Code:
       0: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
       3: ldc           #3                  // String Hello Devoxx
       5: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
       8: return
}

À propos du ByteCode

Environ 200 opérations possibles (maxi. 256 opscodes)
Préfix pour le type d'opérations (i pour entier, d pour double, ...)

Manipulation de la pile, des variables locales (iconst_0, istore, iload, ...)
Contrôle du flux des instructions (if_icmpgt, goto, ...)
Arithmétiques et conversion de type (iadd, iinc, i2d, ...)
Manipulation d'objets (invokevirtual, invokedynamic, ...)
Autres (athrow, ...)

Jouons un peu

Liens

Soyez curieux, regardez comment ça marche avec javap -c !

Introduction Kotlin

Historique

2011 - 2015

Dévoilé par JetBrains
2016

v1.0

Support annoncé par Spring
2017

v1.1 : coroutines, JS, ...

Support annoncé par Google

v1.2 : multiplatform
2018

Kotlin Native 0.6

v1.3 ?
...

Cibles

JVM et Android

JavaScript

Native avec LLVM

HelloWorld.kt

package _00_helloworld

fun main(args: Array<String>) {
    println("Hello Devoxx")
}

kotlinc HelloWorld.kt

kotlinc

hexdump

00000000  ca fe ba be 00 00 00 32  00 33 01 00 1b 5f 30 30  |.......2.3..._00|
00000010  5f 68 65 6c 6c 6f 77 6f  72 6c 64 2f 48 65 6c 6c  |_helloworld/Hell|
00000020  6f 57 6f 72 6c 64 4b 74  07 00 01 01 00 10 6a 61  |oWorldKt......ja|
00000030  76 61 2f 6c 61 6e 67 2f  4f 62 6a 65 63 74 07 00  |va/lang/Object..|
00000040  03 01 00 04 6d 61 69 6e  01 00 16 28 5b 4c 6a 61  |....main...([Lja|
00000050  76 61 2f 6c 61 6e 67 2f  53 74 72 69 6e 67 3b 29  |va/lang/String;)|
00000060  56 01 00 23 4c 6f 72 67  2f 6a 65 74 62 72 61 69  |V..#Lorg/jetbrai|
00000070  6e 73 2f 61 6e 6e 6f 74  61 74 69 6f 6e 73 2f 4e  |ns/annotations/N|
00000080  6f 74 4e 75 6c 6c 3b 01  00 04 61 72 67 73 08 00  |otNull;...args..|
00000090  08 01 00 1e 6b 6f 74 6c  69 6e 2f 6a 76 6d 2f 69  |....kotlin/jvm/i|
000000a0  6e 74 65 72 6e 61 6c 2f  49 6e 74 72 69 6e 73 69  |nternal/Intrinsi|
000000b0  63 73 07 00 0a 01 00 17  63 68 65 63 6b 50 61 72  |cs......checkPar|
000000c0  61 6d 65 74 65 72 49 73  4e 6f 74 4e 75 6c 6c 01  |ameterIsNotNull.|
000000d0  00 27 28 4c 6a 61 76 61  2f 6c 61 6e 67 2f 4f 62  |.'(Ljava/lang/Ob|
000000e0  6a 65 63 74 3b 4c 6a 61  76 61 2f 6c 61 6e 67 2f  |ject;Ljava/lang/|
000000f0  53 74 72 69 6e 67 3b 29  56 0c 00 0c 00 0d 0a 00  |String;)V.......|
00000100  0b 00 0e 01 00 0c 48 65  6c 6c 6f 20 44 65 76 6f  |......Hello Devo|
00000110  78 78 08 00 10 01 00 10  6a 61 76 61 2f 6c 61 6e  |xx......java/lan|
00000120  67 2f 53 79 73 74 65 6d  07 00 12 01 00 03 6f 75  |g/System......ou|
00000130  74 01 00 15 4c 6a 61 76  61 2f 69 6f 2f 50 72 69  |t...Ljava/io/Pri|
00000140  6e 74 53 74 72 65 61 6d  3b 0c 00 14 00 15 09 00  |ntStream;.......|
00000150  13 00 16 01 00 13 6a 61  76 61 2f 69 6f 2f 50 72  |......java/io/Pr|
00000160  69 6e 74 53 74 72 65 61  6d 07 00 18 01 00 07 70  |intStream......p|
00000170  72 69 6e 74 6c 6e 01 00  15 28 4c 6a 61 76 61 2f  |rintln...(Ljava/|
00000180  6c 61 6e 67 2f 4f 62 6a  65 63 74 3b 29 56 0c 00  |lang/Object;)V..|
00000190  1a 00 1b 0a 00 19 00 1c  01 00 13 5b 4c 6a 61 76  |...........[Ljav|
000001a0  61 2f 6c 61 6e 67 2f 53  74 72 69 6e 67 3b 01 00  |a/lang/String;..|
000001b0  11 4c 6b 6f 74 6c 69 6e  2f 4d 65 74 61 64 61 74  |.Lkotlin/Metadat|
000001c0  61 3b 01 00 02 6d 76 03  00 00 00 01 03 00 00 00  |a;...mv.........|
000001d0  09 01 00 02 62 76 03 00  00 00 00 03 00 00 00 02  |....bv..........|
000001e0  01 00 01 6b 01 00 02 64  31 01 00 35 c0 80 12 0a  |...k...d1..5....|
000001f0  c0 80 0a 02 10 02 0a c0  80 0a 02 10 11 0a 02 10  |................|
00000200  0e 0a c0 80 1a 19 10 c0  80 1a 02 30 01 32 0c 10  |...........0.2..|
00000210  02 1a 08 12 04 12 02 30  04 30 03 c2 a2 06 02 10  |.......0.0......|
00000220  05 01 00 02 64 32 01 00  00 01 00 0d 48 65 6c 6c  |....d2......Hell|
00000230  6f 57 6f 72 6c 64 2e 6b  74 01 00 04 43 6f 64 65  |oWorld.kt...Code|
00000240  01 00 12 4c 6f 63 61 6c  56 61 72 69 61 62 6c 65  |...LocalVariable|
00000250  54 61 62 6c 65 01 00 0f  4c 69 6e 65 4e 75 6d 62  |Table...LineNumb|
00000260  65 72 54 61 62 6c 65 01  00 24 52 75 6e 74 69 6d  |erTable..$Runtim|
00000270  65 49 6e 76 69 73 69 62  6c 65 50 61 72 61 6d 65  |eInvisibleParame|
00000280  74 65 72 41 6e 6e 6f 74  61 74 69 6f 6e 73 01 00  |terAnnotations..|
00000290  0a 53 6f 75 72 63 65 46  69 6c 65 01 00 14 53 6f  |.SourceFile...So|
000002a0  75 72 63 65 44 65 62 75  67 45 78 74 65 6e 73 69  |urceDebugExtensi|
000002b0  6f 6e 01 00 19 52 75 6e  74 69 6d 65 56 69 73 69  |on...RuntimeVisi|
000002c0  62 6c 65 41 6e 6e 6f 74  61 74 69 6f 6e 73 00 31  |bleAnnotations.1|
000002d0  00 02 00 04 00 00 00 00  00 01 00 19 00 05 00 06  |................|
000002e0  00 02 00 2c 00 00 00 3f  00 02 00 02 00 00 00 11  |...,...?........|
000002f0  2a 12 09 b8 00 0f 12 11  4c b2 00 17 2b b6 00 1d  |*.......L...+...|
00000300  b1 00 00 00 02 00 2d 00  00 00 0c 00 01 00 00 00  |......-.........|
00000310  11 00 08 00 1e 00 00 00  2e 00 00 00 0a 00 02 00  |................|
00000320  06 00 04 00 10 00 05 00  2f 00 00 00 07 01 00 01  |......../.......|
00000330  00 07 00 00 00 03 00 30  00 00 00 02 00 2b 00 31  |.......0.....+.1|
00000340  00 00 00 63 53 4d 41 50  0a 48 65 6c 6c 6f 57 6f  |...cSMAP.HelloWo|
00000350  72 6c 64 2e 6b 74 0a 4b  6f 74 6c 69 6e 0a 2a 53  |rld.kt.Kotlin.*S|
00000360  20 4b 6f 74 6c 69 6e 0a  2a 46 0a 2b 20 31 20 48  | Kotlin.*F.+ 1 H|
00000370  65 6c 6c 6f 57 6f 72 6c  64 2e 6b 74 0a 5f 30 30  |elloWorld.kt._00|
00000380  5f 68 65 6c 6c 6f 77 6f  72 6c 64 2f 48 65 6c 6c  |_helloworld/Hell|
00000390  6f 57 6f 72 6c 64 4b 74  0a 2a 4c 0a 31 23 31 2c  |oWorldKt.*L.1#1,|
000003a0  35 3a 31 0a 2a 45 0a 00  32 00 00 00 46 00 01 00  |5:1.*E..2...F...|
000003b0  1f 00 05 00 20 5b 00 03  49 00 21 49 00 21 49 00  |.... [..I.!I.!I.|
000003c0  22 00 23 5b 00 03 49 00  21 49 00 24 49 00 25 00  |".#[..I.!I.$I.%.|
000003d0  26 49 00 25 00 27 5b 00  01 73 00 28 00 29 5b 00  |&I.%.'[..s.(.)[.|
000003e0  06 73 00 05 73 00 2a 73  00 08 73 00 2a 73 00 2a  |.s..s.*s..s.*s.*|
000003f0  73 00 06                                          |s..|
000003f3

Java ByteCode

Compiled from "HelloWorld.kt"
public final class _00_helloworld.HelloWorldKt {
  public static final void main(java.lang.String[]);
    Code:
       0: aload_0
       1: ldc           #9                  // String args
       3: invokestatic  #15                 // Method kotlin/jvm/internal/Intrinsics.checkParameterIsNotNull:(Ljava/lang/Object;Ljava/lang/String;)V
       6: ldc           #17                 // String Hello Devoxx
       8: astore_1
       9: getstatic     #23                 // Field java/lang/System.out:Ljava/io/PrintStream;
      12: aload_1
      13: invokevirtual #29                 // Method java/io/PrintStream.println:(Ljava/lang/Object;)V
      16: return
}

HelloWorld-java

package _00_helloworld;

import kotlin.Metadata;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 2,
   d1 = {"\u0000\u0012\n\u0000\n\u0002\u0010\u0002\n\u0000\n\u0002\u0010\u0011\n\u0002\u0010\u000e\n\u0000\u001a\u0019\u0010\u0000\u001a\u00020\u00012\f\u0010\u0002\u001a\b\u0012\u0004\u0012\u00020\u00040\u0003¢\u0006\u0002\u0010\u0005"},
   d2 = {"main", "", "args", "", "", "([Ljava/lang/String;)V"}
)
public final class HelloWorldKt {
   public static final void main(@NotNull String[] args) {
      Intrinsics.checkParameterIsNotNull(args, "args");
      String var1 = "Hello Devoxx";
      System.out.println(var1);
   }
}

Bilan HelloWorld.kt

👮‍♂️ Kotlin ajoute des contrôles
du coup on a besoin de JARs en plus

jar	taille
kotlin-stdlib-1.2.31.jar	919K
kotlin-stdlib-jdk7-1.2.31.jar	3.1K
kotlin-stdlib-jdk8-1.2.31.jar	13K
kotlin-reflect-1.2.31.jar	2.5M
guava-18.0.jar	2.2M
lombok-1.16.18.jar	1.4M
spring-core-5.0.5.RELEASE.jar	1.2M
jackson-databind-2.9.5.jar	1.3M

🏎 Performances ?

Performance HelloWorld.kt

Ne croyez pas les benchmarks, faites les vous-même !

Benchmark	Mode	Cnt	Score	Error	Units
testJava	thrpt	200	66490.271	± 879.996	ops/s
testKotlin	thrpt	200	72393.914	± 935.962	ops/s

Les bases

val-var.kt

var x: Int = 10
val y: Int = 3
x += 4
// y += 4 <== 💣 Compilation Error

println(x * y) // 42

string-template.kt

fun greeting(who: Someone) {
    println("Hello $who!")
    println("Hello ${who.firstName} ${who.lastName}!")
}

string-template.java

package _01_basic;

import kotlin.Metadata;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 2,
   d1 = {"\u0000\f\n\u0000\n\u0002\u0010\u0002\n\u0000\n\u0002\u0018\u0002\u001a\u000e\u0010\u0000\u001a\u00020\u00012\u0006\u0010\u0002\u001a\u00020\u0003"},
   d2 = {"greeting", "", "who", "L_01_basic/Someone;"}
)
public final class String_templatesKt {
   public static final void greeting(@NotNull Someone who) {
      Intrinsics.checkParameterIsNotNull(who, "who");
      String var1 = "Hello " + who + '!';
      System.out.println(var1);
      var1 = "Hello " + who.getFirstName() + ' ' + who.getLastName() + '!';
      System.out.println(var1);
   }
}

ByteCode de string-template

Compiled from "string-templates.kt"
public final class _01_basic.String_templatesKt {
  public static final void greeting(_01_basic.Someone);
    Code:
       0: aload_0
       1: ldc           #9                  // String who
       3: invokestatic  #15                 // Method kotlin/jvm/internal/Intrinsics.checkParameterIsNotNull:(Ljava/lang/Object;Ljava/lang/String;)V
       6: new           #17                 // class java/lang/StringBuilder
       9: dup
      10: invokespecial #21                 // Method java/lang/StringBuilder."<init>":()V
      13: ldc           #23                 // String Hello
      15: invokevirtual #27                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      18: aload_0
      19: invokevirtual #30                 // Method java/lang/StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
      22: bipush        33
      24: invokevirtual #33                 // Method java/lang/StringBuilder.append:(C)Ljava/lang/StringBuilder;
      27: invokevirtual #37                 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
      30: astore_1
      31: getstatic     #43                 // Field java/lang/System.out:Ljava/io/PrintStream;
      34: aload_1
      35: invokevirtual #49                 // Method java/io/PrintStream.println:(Ljava/lang/Object;)V
      38: new           #17                 // class java/lang/StringBuilder
      41: dup
      42: invokespecial #21                 // Method java/lang/StringBuilder."<init>":()V
      45: ldc           #23                 // String Hello
      47: invokevirtual #27                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      50: aload_0
      51: invokevirtual #54                 // Method _01_basic/Someone.getFirstName:()Ljava/lang/String;
      54: invokevirtual #27                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      57: bipush        32
      59: invokevirtual #33                 // Method java/lang/StringBuilder.append:(C)Ljava/lang/StringBuilder;
      62: aload_0
      63: invokevirtual #57                 // Method _01_basic/Someone.getLastName:()Ljava/lang/String;
      66: invokevirtual #27                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      69: bipush        33
      71: invokevirtual #33                 // Method java/lang/StringBuilder.append:(C)Ljava/lang/StringBuilder;
      74: invokevirtual #37                 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
      77: astore_1
      78: getstatic     #43                 // Field java/lang/System.out:Ljava/io/PrintStream;
      81: aload_1
      82: invokevirtual #49                 // Method java/io/PrintStream.println:(Ljava/lang/Object;)V
      85: return
}

numeric.kt

val anInt = 42  // type inference: Int
val aLong = 42L // type inference: Long
var aDouble: Double? = null

numeric.java

package _01_basic;

import kotlin.Metadata;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 2,
   d1 = {"\u0000\u0006\n\u0000\n\u0002\u0010\u0002\u001a\u0006\u0010\u0000\u001a\u00020\u0001"},
   d2 = {"tryNumeric", ""}
)
public final class NumericKt {
   public static final void tryNumeric() {
      int anInt = true;
      long aLong = 42L;
      Double aDouble = (Double)null;
   }
}

ByteCode de numeric

Compiled from "numeric.kt"
public final class _01_basic.NumericKt {
  public static final void tryNumeric();
    Code:
       0: bipush        42
       2: istore_0
       3: ldc2_w        #7                  // long 42l
       6: lstore_1
       7: aconst_null
       8: checkcast     #10                 // class java/lang/Double
      11: astore_3
      12: return
}

C'est simple

Plus de ; ^*
😍 String templating
😘 Plus de types primitifs (avant la compilation)
🧐 Inférence de type
On peut mélanger du code Java et Kotlin

null-safety

billion-dollar mistake

I call it my billion-dollar mistake. It was the invention of the null reference in 1965. At that time, I was designing the first comprehensive type system for references in an object oriented language (ALGOL W). My goal was to ensure that all use of references should be absolutely safe, with checking performed automatically by the compiler. But I couldn't resist the temptation to put in a null reference, simply because it was so easy to implement. This has led to innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years.

--Tony Hoare (C.A.R. Hoare)

Null References: The Billion Dollar Mistake

null-safety.kt

fun main(args: Array<String>) {

    val somethingNotNull: String = "aString"
    // somethingNotNull: String = null => compilation error

    var length = somethingNotNull.length

    var something: String? = null
    length = something?.length ?: 0

    length = something()?.length ?: 0

    // length = something()!!.length // throw kotlin.KotlinNullPointerException

    // SmartCast
    something = "aString"
    length = something.length
}

fun something(): String? = null

null-safety.java

package _02_null_safety;

import kotlin.Metadata;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

@Metadata(
        mv = {1, 1, 9},
        bv = {1, 0, 2},
        k = 2,
        d1 = {"\u0000\u0014\n\u0000\n\u0002\u0010\u0002\n\u0000\n\u0002\u0010\u0011\n\u0002\u0010\u000e\n\u0002\b\u0002\u001a\u0019\u0010\u0000\u001a\u00020\u00012\f\u0010\u0002\u001a\b\u0012\u0004\u0012\u00020\u00040\u0003¢\u0006\u0002\u0010\u0005\u001a\b\u0010\u0006\u001a\u0004\u0018\u00010\u0004"},
        d2 = {"main", "", "args", "", "", "([Ljava/lang/String;)V", "something"}
)
public final class NullSafetyKt {
   public static final void main(@NotNull String[] args) {
      Intrinsics.checkParameterIsNotNull(args, "args");
      String somethingNotNull = "aString";
      int length = somethingNotNull.length();
      String something = (String)null;
      int length = false;
      String var10000 = something();
      length = var10000 != null ? var10000.length() : 0;
      var10000 = something();
      if (var10000 == null) {
         Intrinsics.throwNpe();
      }

      length = var10000.length();
      something = "aString";
      length = something.length();
   }

   @Nullable
   public static final String something() {
      return null;
   }
}

Bilan null-safety

🎸 Elvis operator: ?:
🙌 plus de NullPointerException
⚠️ quand on appel du Java

Les types

Types basiques

Types basiques nullable

todo.kt

fun `is P = NP`(): Boolean =
    TODO()

fun main(args: Array<String>) {
    println("P = NP is ${`is P = NP`()}")
}

Hierarchie des types

🤝 le TODO() est l'ami du TDD

Les fonctions

named-params.kt

fun buildString(prefix: String,
                who: String,
                enhanced: Boolean): String {
    var msg = "$prefix $who"
    if (enhanced) {
        msg += '!'
    }
    return msg
}

fun greetings(): String =
    buildString(enhanced = true, who = "Devoxx", prefix = "Hello")

named-params.java

package _03_fun;

import kotlin.Metadata;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 2,
   d1 = {"\u0000\u0010\n\u0000\n\u0002\u0010\u000e\n\u0002\b\u0003\n\u0002\u0010\u000b\n\u0000\u001a\u001e\u0010\u0000\u001a\u00020\u00012\u0006\u0010\u0002\u001a\u00020\u00012\u0006\u0010\u0003\u001a\u00020\u00012\u0006\u0010\u0004\u001a\u00020\u0005\u001a\u0006\u0010\u0006\u001a\u00020\u0001"},
   d2 = {"buildString", "", "prefix", "who", "enhanced", "", "greetings"}
)
public final class NamedKt {
   @NotNull
   public static final String buildString(@NotNull String prefix, @NotNull String who, boolean enhanced) {
      Intrinsics.checkParameterIsNotNull(prefix, "prefix");
      Intrinsics.checkParameterIsNotNull(who, "who");
      String msg = "" + prefix + ' ' + who;
      if (enhanced) {
         msg = msg + '!';
      }

      return msg;
   }

   @NotNull
   public static final String greetings() {
      String var0 = "Hello";
      String var1 = "Devoxx";
      boolean var2 = true;
      return buildString(var0, var1, var2);
   }
}

default-value.kt

fun buildString2(prefix: String = "Hello",
                 who: String,
                 enhanced: Boolean = true): String {
    var msg = "$prefix $who"
    if (enhanced) {
        msg += '!'
    }
    return msg
}

fun greetings2(): String =
    buildString2(who = "Devoxx")

default-value.java

package _03_fun;

import kotlin.Metadata;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 2,
   d1 = {"\u0000\u0010\n\u0000\n\u0002\u0010\u000e\n\u0002\b\u0003\n\u0002\u0010\u000b\n\u0000\u001a\"\u0010\u0000\u001a\u00020\u00012\b\b\u0002\u0010\u0002\u001a\u00020\u00012\u0006\u0010\u0003\u001a\u00020\u00012\b\b\u0002\u0010\u0004\u001a\u00020\u0005\u001a\u0006\u0010\u0006\u001a\u00020\u0001"},
   d2 = {"buildString2", "", "prefix", "who", "enhanced", "", "greetings2"}
)
public final class Default_valueKt {
   @NotNull
   public static final String buildString2(@NotNull String prefix, @NotNull String who, boolean enhanced) {
      Intrinsics.checkParameterIsNotNull(prefix, "prefix");
      Intrinsics.checkParameterIsNotNull(who, "who");
      String msg = "" + prefix + ' ' + who;
      if (enhanced) {
         msg = msg + '!';
      }

      return msg;
   }

   @NotNull
   public static final String greetings2() {
      return buildString2$default((String)null, "Devoxx", false, 5, (Object)null);
   }
}

ByteCode de default-value

Compiled from "default-value.kt"
public final class _03_fun.Default_valueKt {
  public static final java.lang.String buildString2(java.lang.String, java.lang.String, boolean);
    Code:
       0: aload_0
       1: ldc           #9                  // String prefix
       3: invokestatic  #15                 // Method kotlin/jvm/internal/Intrinsics.checkParameterIsNotNull:(Ljava/lang/Object;Ljava/lang/String;)V
       6: aload_1
       7: ldc           #17                 // String who
       9: invokestatic  #15                 // Method kotlin/jvm/internal/Intrinsics.checkParameterIsNotNull:(Ljava/lang/Object;Ljava/lang/String;)V
      12: new           #19                 // class java/lang/StringBuilder
      15: dup
      16: invokespecial #23                 // Method java/lang/StringBuilder."<init>":()V
      19: ldc           #25                 // String
      21: invokevirtual #29                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      24: aload_0
      25: invokevirtual #29                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      28: bipush        32
      30: invokevirtual #32                 // Method java/lang/StringBuilder.append:(C)Ljava/lang/StringBuilder;
      33: aload_1
      34: invokevirtual #29                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      37: invokevirtual #36                 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
      40: astore_3
      41: iload_2
      42: ifeq          66
      45: aload_3
      46: new           #19                 // class java/lang/StringBuilder
      49: dup
      50: invokespecial #23                 // Method java/lang/StringBuilder."<init>":()V
      53: swap
      54: invokevirtual #29                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
      57: bipush        33
      59: invokevirtual #32                 // Method java/lang/StringBuilder.append:(C)Ljava/lang/StringBuilder;
      62: invokevirtual #36                 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
      65: astore_3
      66: aload_3
      67: areturn

  public static java.lang.String buildString2$default(java.lang.String, java.lang.String, boolean, int, java.lang.Object);
    Code:
       0: iload_3
       1: iconst_1
       2: iand
       3: ifeq          9
       6: ldc           #46                 // String Hello
       8: astore_0
       9: iload_3
      10: iconst_4
      11: iand
      12: ifeq          17
      15: iconst_1
      16: istore_2
      17: aload_0
      18: aload_1
      19: iload_2
      20: invokestatic  #48                 // Method buildString2:(Ljava/lang/String;Ljava/lang/String;Z)Ljava/lang/String;
      23: areturn

  public static final java.lang.String greetings2();
    Code:
       0: aconst_null
       1: ldc           #51                 // String Devoxx
       3: iconst_0
       4: iconst_5
       5: aconst_null
       6: invokestatic  #53                 // Method buildString2$default:(Ljava/lang/String;Ljava/lang/String;ZILjava/lang/Object;)Ljava/lang/String;
       9: areturn
}

C'est `fun` !

✨ Conseils

Toujours typer le retour de vos fonctions (sauf si c'est évident et une surcharge comme le toString)
Kotlin est plus expressif que Java => évitez de faire des fonctions trop longues
Sautez une ligne après le =
Utilisez le passage des arguments par nom quand ça lève des ambiguïtés

📝 Notes

Le passage des arguments par nom, ne marche pas sur les appels de code Java

Les lambdas

function.kt

// Declare apply function with function as parameter
fun apply(x: Int, y: Int, operation: (Int, Int) -> Int): Int =
    operation(x, y)

// Declare function
fun sumf(x: Int, y: Int) : Int =
    x + y

// call apply with function reference
val sum5 = apply(2,3, ::sumf)

// store function reference
val sumLam = ::sumf

// call apply with the function reference
val sum6 = apply(1,5, sumLam)

function.java

package _04_lamda;

import kotlin.Metadata;
import kotlin.jvm.functions.Function2;
import kotlin.jvm.internal.Intrinsics;
import kotlin.reflect.KFunction;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 2,
   d1 = {"\u0000\u001c\n\u0000\n\u0002\u0010\b\n\u0002\b\u0005\n\u0002\u0018\u0002\n\u0002\u0018\u0002\n\u0002\b\u0007\n\u0002\u0018\u0002\n\u0000\u001a0\u0010\u000e\u001a\u00020\u00012\u0006\u0010\n\u001a\u00020\u00012\u0006\u0010\u000b\u001a\u00020\u00012\u0018\u0010\u000f\u001a\u0014\u0012\u0004\u0012\u00020\u0001\u0012\u0004\u0012\u00020\u0001\u0012\u0004\u0012\u00020\u00010\u0010\u001a\u0016\u0010\u0011\u001a\u00020\u00012\u0006\u0010\n\u001a\u00020\u00012\u0006\u0010\u000b\u001a\u00020\u0001\"\u0011\u0010\u0000\u001a\u00020\u0001¢\u0006\b\n\u0000\u001a\u0004\b\u0002\u0010\u0003\"\u0011\u0010\u0004\u001a\u00020\u0001¢\u0006\b\n\u0000\u001a\u0004\b\u0005\u0010\u0003\"A\u0010\u0006\u001a2\u0012\u0013\u0012\u00110\u0001¢\u0006\f\b\b\u0012\b\b\t\u0012\u0004\b\b(\n\u0012\u0013\u0012\u00110\u0001¢\u0006\f\b\b\u0012\b\b\t\u0012\u0004\b\b(\u000b\u0012\u0004\u0012\u00020\u00010\u0007¢\u0006\b\n\u0000\u001a\u0004\b\f\u0010\r"},
   d2 = {"sum5", "", "getSum5", "()I", "sum6", "getSum6", "sumLam", "Lkotlin/reflect/KFunction2;", "Lkotlin/ParameterName;", "name", "x", "y", "getSumLam", "()Lkotlin/reflect/KFunction;", "apply", "operation", "Lkotlin/Function2;", "sumf"}
)
public final class FunctionKt {
   private static final int sum5;
   @NotNull
   private static final KFunction sumLam;
   private static final int sum6;

   public static final int apply(int x, int y, @NotNull Function2 operation) {
      Intrinsics.checkParameterIsNotNull(operation, "operation");
      return ((Number)operation.invoke(x, y)).intValue();
   }

   public static final int sumf(int x, int y) {
      return x + y;
   }

   public static final int getSum5() {
      return sum5;
   }

   @NotNull
   public static final KFunction getSumLam() {
      return sumLam;
   }

   public static final int getSum6() {
      return sum6;
   }

   static {
      sum5 = apply(2, 3, (Function2)null.INSTANCE);
      sumLam = null.INSTANCE;
      sum6 = apply(1, 5, (Function2)sumLam);
   }
}

lambda.kt

// Declare lambda
val suml: (Int, Int) -> Int = { x: Int, y: Int -> x + y }

// call apply with suml lambda
val sum3 = apply(1, 2, suml)

// call apply with lamda
val sum4 = apply(1, 3) { x, y -> x + y }

lambda.java

package _04_lamda;

import kotlin.Metadata;
import kotlin.jvm.functions.Function2;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 2,
   d1 = {"\u0000\u0012\n\u0000\n\u0002\u0010\b\n\u0002\b\u0005\n\u0002\u0018\u0002\n\u0002\b\u0002\"\u0011\u0010\u0000\u001a\u00020\u0001¢\u0006\b\n\u0000\u001a\u0004\b\u0002\u0010\u0003\"\u0011\u0010\u0004\u001a\u00020\u0001¢\u0006\b\n\u0000\u001a\u0004\b\u0005\u0010\u0003\"#\u0010\u0006\u001a\u0014\u0012\u0004\u0012\u00020\u0001\u0012\u0004\u0012\u00020\u0001\u0012\u0004\u0012\u00020\u00010\u0007¢\u0006\b\n\u0000\u001a\u0004\b\b\u0010\t"},
   d2 = {"sum3", "", "getSum3", "()I", "sum4", "getSum4", "suml", "Lkotlin/Function2;", "getSuml", "()Lkotlin/jvm/functions/Function2;"}
)
public final class LambdaKt {
   @NotNull
   private static final Function2 suml;
   private static final int sum3;
   private static final int sum4;

   @NotNull
   public static final Function2 getSuml() {
      return suml;
   }

   public static final int getSum3() {
      return sum3;
   }

   public static final int getSum4() {
      return sum4;
   }

   static {
      suml = (Function2)null.INSTANCE;
      sum3 = FunctionKt.apply(1, 2, suml);
      sum4 = FunctionKt.apply(1, 3, (Function2)null.INSTANCE);
   }
}

let.kt

val other = sumf(1,2)
    .let { it + 1 }

val nullable = maybeAnInt()
    ?.let { it + 1 }

let.java

package _04_lamda;

import kotlin.Metadata;
import kotlin.NotImplementedError;
import kotlin.jvm.internal.DefaultConstructorMarker;
import org.jetbrains.annotations.Nullable;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 2,
   d1 = {"\u0000\n\n\u0000\n\u0002\u0010\b\n\u0002\b\u0007\u001a\r\u0010\b\u001a\u0004\u0018\u00010\u0001¢\u0006\u0002\u0010\u0003\"\u0015\u0010\u0000\u001a\u0004\u0018\u00010\u0001¢\u0006\n\n\u0002\u0010\u0004\u001a\u0004\b\u0002\u0010\u0003\"\u0011\u0010\u0005\u001a\u00020\u0001¢\u0006\b\n\u0000\u001a\u0004\b\u0006\u0010\u0007"},
   d2 = {"nullable", "", "getNullable", "()Ljava/lang/Integer;", "Ljava/lang/Integer;", "other", "getOther", "()I", "maybeAnInt"}
)
public final class LetKt {
   private static final int other;
   @Nullable
   private static final Integer nullable;

   @Nullable
   public static final Integer maybeAnInt() {
      throw (Throwable)(new NotImplementedError((String)null, 1, (DefaultConstructorMarker)null));
   }

   public static final int getOther() {
      return other;
   }

   @Nullable
   public static final Integer getNullable() {
      return nullable;
   }

   static {
      int var0 = FunctionKt.sumf(1, 2);
      other = var0 + 1;
      Integer var10000 = maybeAnInt();
      if (var10000 != null) {
         Integer var3 = var10000;
         int it = ((Number)var3).intValue();
         var10000 = it + 1;
      } else {
         var10000 = null;
      }

      nullable = var10000;
   }
}

Les lambdas

⚠️ pas de return
pensez à mettre vos lambda comme dernier argument
voir aussi les apply, also, run , use, with
- the tldr; on Kotlin’s let, apply, also, with and run functions

Les classes

astronomy.kt

interface AstronomicalBody {
    val name: String
}

data class Planet(override val name: String,
                  val moons: List<Moon> = emptyList()) : AstronomicalBody {
    init {
        require(name.isNotEmpty())
    }

    operator fun plus(moon: Moon): Planet {
        return this.copy(moons = kotlin.collections.listOf(moon))
    }
}

data class Moon(override val name: String) : AstronomicalBody

object SolarSystem {
    val earth = Planet(name = "Earth")
    val moon = Moon(name = "Moon")

    val bodies: List<AstronomicalBody> = listOf(
        earth,
        Planet(name = "Jupiter")
    )
}

enum class PlanetKind {
    Terrestrial, GasGiant, IceGiant;

    companion object {
        fun fromName(name: String): PlanetKind {
            return PlanetKind.valueOf(name) // enumValueOf(name)
        }
    }
}

fun getMoons(planet: Planet): List<Moon> {
    val (_, moons) = planet
    return moons
}

astronomy.java

package _05_class_1;

import java.util.List;
import kotlin.Metadata;
import kotlin.collections.CollectionsKt;
import kotlin.jvm.internal.DefaultConstructorMarker;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 1,
   d1 = {"\u00000\n\u0002\u0018\u0002\n\u0002\u0018\u0002\n\u0000\n\u0002\u0010\u000e\n\u0000\n\u0002\u0010 \n\u0002\u0018\u0002\n\u0002\b\t\n\u0002\u0010\u000b\n\u0000\n\u0002\u0010\u0000\n\u0000\n\u0002\u0010\b\n\u0002\b\u0003\b\u0086\b\u0018\u00002\u00020\u0001B\u001d\u0012\u0006\u0010\u0002\u001a\u00020\u0003\u0012\u000e\b\u0002\u0010\u0004\u001a\b\u0012\u0004\u0012\u00020\u00060\u0005¢\u0006\u0002\u0010\u0007J\t\u0010\f\u001a\u00020\u0003HÆ\u0003J\u000f\u0010\r\u001a\b\u0012\u0004\u0012\u00020\u00060\u0005HÆ\u0003J#\u0010\u000e\u001a\u00020\u00002\b\b\u0002\u0010\u0002\u001a\u00020\u00032\u000e\b\u0002\u0010\u0004\u001a\b\u0012\u0004\u0012\u00020\u00060\u0005HÆ\u0001J\u0013\u0010\u000f\u001a\u00020\u00102\b\u0010\u0011\u001a\u0004\u0018\u00010\u0012HÖ\u0003J\t\u0010\u0013\u001a\u00020\u0014HÖ\u0001J\u0011\u0010\u0015\u001a\u00020\u00002\u0006\u0010\u0016\u001a\u00020\u0006H\u0086\u0002J\t\u0010\u0017\u001a\u00020\u0003HÖ\u0001R\u0017\u0010\u0004\u001a\b\u0012\u0004\u0012\u00020\u00060\u0005¢\u0006\b\n\u0000\u001a\u0004\b\b\u0010\tR\u0014\u0010\u0002\u001a\u00020\u0003X\u0096\u0004¢\u0006\b\n\u0000\u001a\u0004\b\n\u0010\u000b"},
   d2 = {"L_05_class_1/Planet;", "L_05_class_1/AstronomicalBody;", "name", "", "moons", "", "L_05_class_1/Moon;", "(Ljava/lang/String;Ljava/util/List;)V", "getMoons", "()Ljava/util/List;", "getName", "()Ljava/lang/String;", "component1", "component2", "copy", "equals", "", "other", "", "hashCode", "", "plus", "moon", "toString"}
)
public final class Planet implements AstronomicalBody {
   @NotNull
   private final String name;
   @NotNull
   private final List moons;

   @NotNull
   public final Planet plus(@NotNull Moon moon) {
      Intrinsics.checkParameterIsNotNull(moon, "moon");
      return copy$default(this, (String)null, CollectionsKt.listOf(moon), 1, (Object)null);
   }

   @NotNull
   public String getName() {
      return this.name;
   }

   @NotNull
   public final List getMoons() {
      return this.moons;
   }

   public Planet(@NotNull String name, @NotNull List moons) {
      Intrinsics.checkParameterIsNotNull(name, "name");
      Intrinsics.checkParameterIsNotNull(moons, "moons");
      super();
      this.name = name;
      this.moons = moons;
      CharSequence var3 = (CharSequence)this.getName();
      boolean var5 = var3.length() > 0;
      if (!var5) {
         String var4 = "Failed requirement.";
         throw (Throwable)(new IllegalArgumentException(var4.toString()));
      }
   }

   // $FF: synthetic method
   public Planet(String var1, List var2, int var3, DefaultConstructorMarker var4) {
      if ((var3 & 2) != 0) {
         var2 = CollectionsKt.emptyList();
      }

      this(var1, var2);
   }

   @NotNull
   public final String component1() {
      return this.getName();
   }

   @NotNull
   public final List component2() {
      return this.moons;
   }

   @NotNull
   public final Planet copy(@NotNull String name, @NotNull List moons) {
      Intrinsics.checkParameterIsNotNull(name, "name");
      Intrinsics.checkParameterIsNotNull(moons, "moons");
      return new Planet(name, moons);
   }

   public String toString() {
      return "Planet(name=" + this.getName() + ", moons=" + this.moons + ")";
   }

   public int hashCode() {
      String var10000 = this.getName();
      return (var10000 != null ? var10000.hashCode() : 0) * 31 + (this.moons != null ? this.moons.hashCode() : 0);
   }

   public boolean equals(Object var1) {
      if (this != var1) {
         if (var1 instanceof Planet) {
            Planet var2 = (Planet)var1;
            if (Intrinsics.areEqual(this.getName(), var2.getName()) && Intrinsics.areEqual(this.moons, var2.moons)) {
               return true;
            }
         }

         return false;
      } else {
         return true;
      }
   }
}

Héritage en Kotlin

open class SmallBody {
    open fun sizeRange(): IntRange = 0..10
}

data class Comet(val name: String) : SmallBody()

data class Asteroid(val name: String) : SmallBody() {
    override fun sizeRange(): IntRange = 0..4
}

fun main(args: Array<String>) {
    val bodies = listOf(Comet("Halley"), Asteroid("Adeona"))

    bodies.forEach { body ->
        println("$body: ${body.sizeRange()}")
    }
}

Génériques

⚠️ Les contrôles de types génériques ne sont fait qu'au moment de la compilation
Covariant: out, en java ? extends T
Contravariant: in, en java ? super T

Borne supérieure

fun <T : Comparable<T>> sort(list: List<T>): List<T>

Les détails: https://kotlinlang.org/docs/reference/generics.html

Projection `*`

interface Function<in T, out U>

Function<*, String> // correspond à Function<in Nothing, String>

Function<Int, *> // correspond à Function<Int, out Any?>

Function<*, *> // correspond à Function<in Nothing, out Any?>

Sealed

sealed class JsonValue

data class JsonObject(val attributes: Map<String, JsonValue>) : JsonValue()
data class JsonArray(val values: List<JsonValue>) : JsonValue()
data class JsonString(val value: String) : JsonValue()
data class JsonNumber(val value: Number) : JsonValue()
data class JsonBoolean(val value: Boolean) : JsonValue()
object JsonNull : JsonValue()

Alias en Kotlin

interface Entity

typealias Id = String
typealias Version = Int
typealias EntityKey = Pair<Id, Version>

// fun getAllEntities(): Map<Pair<String, Int>, List<Entity>> = emptyMap()
fun getAllEntities(): Map<EntityKey, List<Entity>> = emptyMap()

ByteCode d'alias

Compiled from "typealias.kt"
public final class _06_class_2.TypealiasKt {
  public static final java.util.Map<kotlin.Pair<java.lang.String, java.lang.Integer>, java.util.List<_06_class_2.Entity>> getAllEntities();
    Code:
       0: invokestatic  #12                 // Method kotlin/collections/MapsKt.emptyMap:()Ljava/util/Map;
       3: areturn
}

Classe, le bilan

🤩 data class
🤔 Mais pourquoi on n'a pas ça en Java ?
Une seule classe par fichier n'est pas utile
🤓 sealed permet de faire des types algébriques de données (Algebraic Data Type)

Pause

ByteCode Android

Compilation pour Android

Dalvik EXecutable format

Dalvik Executable format

java -jar ./scripts/lib/d8.jar --release \
            --output ./target/android/dex \
            ./target/android/hello.jar

00000000  64 65 78 0a 30 33 35 00  06 50 f0 61 50 10 7c c0  |dex.035..P.aP.|.|
00000010  b2 f9 77 2d 54 df 60 f3  ac dd b0 10 eb 55 53 e1  |..w-T.`......US.|
00000020  28 f6 10 00 70 00 00 00  78 56 34 12 00 00 00 00  |(...p...xV4.....|
00000030  00 00 00 00 4c f5 10 00  12 17 00 00 70 00 00 00  |....L.......p...|
00000040  31 03 00 00 b8 5c 00 00  2a 08 00 00 7c 69 00 00  |1....\..*...|i..|
00000050  30 03 00 00 74 cb 00 00  20 1a 00 00 f4 e4 00 00  |0...t... .......|
00000060  75 02 00 00 f4 b5 01 00  94 f1 0e 00 94 04 02 00  |u...............|
00000070  4a f1 07 00 4c f1 07 00  75 f1 07 00 a4 f1 07 00  |J...L...u.......|
00000080  c2 f1 07 00 e0 f1 07 00  00 f2 07 00 23 f2 07 00  |............#...|
00000090  71 f2 07 00 b9 f2 07 00  07 f3 07 00 37 f3 07 00  |q...........7...|
000000a0  69 f3 07 00 90 f3 07 00  bc f3 07 00 e3 f3 07 00  |i...............|
000000b0  27 f4 07 00 71 f4 07 00  8f f4 07 00 ad f4 07 00  |'...q...........|
000000c0  cb f4 07 00 ed f4 07 00  0f f5 07 00 2c f5 07 00  |............,...|
000000d0  49 f5 07 00 79 f5 07 00  b1 f5 07 00 e9 f5 07 00  |I...y...........|
000000e0  1a f6 07 00 51 f6 07 00  7b f6 07 00 a6 f6 07 00  |....Q...{.......|
000000f0  d1 f6 07 00 0a f7 07 00  47 f7 07 00 84 f7 07 00  |........G.......|
00000100  c1 f7 07 00 02 f8 07 00  43 f8 07 00 84 f8 07 00  |........C.......|
00000110  f1 f8 07 00 12 f9 07 00  41 f9 07 00 6e f9 07 00  |........A...n...|
00000120  b0 f9 07 00 dd f9 07 00  0a fa 07 00 39 fa 07 00  |............9...|
00000130  68 fa 07 00 ab fa 07 00  e0 fa 07 00 25 fb 07 00  |h...........%...|
00000140  f3 fb 07 00 3b fc 07 00  79 fc 07 00 b1 fc 07 00  |....;...y.......|
00000150  eb fc 07 00 26 fd 07 00  68 fd 07 00 9e fd 07 00  |....&...h.......|
00000160  e7 fd 07 00 2a fe 07 00  5c fe 07 00 9d fe 07 00  |....*...\.......|
00000170  de fe 07 00 25 ff 07 00  5b ff 07 00 90 ff 07 00  |....%...[.......|
00000180  c0 ff 07 00 fc ff 07 00  75 00 08 00 ca 00 08 00  |........u.......|
00000190  30 01 08 00 a7 01 08 00  2f 02 08 00 c9 02 08 00  |0......./.......|
000001a0  74 03 08 00 30 04 08 00  fd 04 08 00 db 05 08 00  |t...0...........|
000001b0  ca 06 08 00 ca 07 08 00  db 08 08 00 fd 09 08 00  |................|
000001c0  30 0b 08 00 76 0c 08 00  cd 0d 08 00 35 0f 08 00  |0...v.......5...|
000001d0  ae 10 08 00 38 12 08 00  d3 13 08 00 7f 15 08 00  |....8...........|
000001e0  3c 17 08 00 7b 17 08 00  b8 17 08 00 f5 17 08 00  |<...{...........|
000001f0  34 18 08 00 80 18 08 00  cc 18 08 00 18 19 08 00  |4...............|
00000200  64 19 08 00 b0 19 08 00  fc 19 08 00 48 1a 08 00  |d...........H...|
00000210  94 1a 08 00 c8 1a 08 00  ff 1a 08 00 3f 1b 08 00  |............?...|
00000220  87 1b 08 00 62 1c 08 00  a8 1c 08 00 16 1d 08 00  |....b...........|
00000230  57 1d 08 00 a4 1d 08 00  e8 1d 08 00 31 1e 08 00  |W...........1...|
00000240  86 1e 08 00 d1 1e 08 00  23 1f 08 00 7a 1f 08 00  |........#...z...|
00000250  bf 1f 08 00 06 20 08 00  4d 20 08 00 f8 20 08 00  |..... ..M ... ..|
00000260  4f 21 08 00 84 21 08 00  b9 21 08 00 f8 21 08 00  |O!...!...!...!..|
00000270  4e 22 08 00 9d 22 08 00  e7 22 08 00 21 23 08 00  |N"..."..."..!#..|
00000280  6b 23 08 00 d2 23 08 00  0e 24 08 00 4a 24 08 00  |k#...#...$..J$..|
00000290  8d 24 08 00 e1 24 08 00  43 25 08 00 c6 25 08 00  |.$...$..C%...%..|
000002a0  14 26 08 00 6c 26 08 00  b9 26 08 00 0c 27 08 00  |.&..l&...&...'..|
000002b0  61 27 08 00 9f 27 08 00  e3 27 08 00 55 28 08 00  |a'...'...'..U(..|
000002c0  d1 28 08 00 2a 29 08 00  db 29 08 00 8c 2a 08 00  |.(..*)...)...*..|
000002d0  e5 2a 08 00 3e 2b 08 00  97 2b 08 00 e6 2b 08 00  |.*..>+...+...+..|
000002e0  8c 2c 08 00 a5 2f 08 00  ed 2f 08 00 1a 31 08 00  |.,.../.../...1..|
000002f0  6f 31 08 00 c4 31 08 00  31 32 08 00 88 32 08 00  |o1...1..12...2..|
00000300  fa 32 08 00 87 33 08 00  2c 34 08 00 75 34 08 00  |.2...3..,4..u4..|
00000310  da 34 08 00 85 35 08 00  ed 35 08 00 50 36 08 00  |.4...5...5..P6..|
00000320  a1 36 08 00 fe 36 08 00  48 37 08 00 8e 37 08 00  |.6...6..H7...7..|
00000330  ce 37 08 00 6f 38 08 00  dc 38 08 00 23 39 08 00  |.7..o8...8..#9..|
00000340  64 39 08 00 a1 39 08 00  f4 39 08 00 47 3a 08 00  |d9...9...9..G:..|
00000350  b1 3a 08 00 0f 3b 08 00  ae 3b 08 00 5a 3c 08 00  |.:...;...;..Z<..|
00000360  e4 3c 08 00 c0 3d 08 00  4a 3e 08 00 ae 3e 08 00  |.<...=..J>...>..|
00000370  0f 3f 08 00 b0 3f 08 00  83 40 08 00 f4 40 08 00  |.?...?...@...@..|
00000380  3f 41 08 00 8b 41 08 00  06 42 08 00 6d 42 08 00  |?A...A...B..mB..|
00000390  14 43 08 00 a7 43 08 00  0e 44 08 00 75 44 08 00  |.C...C...D..uD..|
000003a0  41 45 08 00 9b 45 08 00  f5 45 08 00 61 46 08 00  |AE...E...E..aF..|
000003b0  14 47 08 00 c7 47 08 00  25 48 08 00 78 48 08 00  |.G...G..%H..xH..|
000003c0  11 49 08 00 d7 49 08 00  44 4a 08 00 b3 4a 08 00  |.I...I..DJ...J..|
000003d0  20 4b 08 00 b1 4b 08 00  d7 4d 08 00 58 4e 08 00  | K...K...M..XN..|
000003e0  f5 4e 08 00 99 4f 08 00  36 50 08 00 cd 50 08 00  |.N...O..6P...P..|
000003f0  44 51 08 00 c4 51 08 00  3d 52 08 00 af 52 08 00  |DQ...Q..=R...R..|
00000400  2c 53 08 00 aa 53 08 00  15 54 08 00 af 54 08 00  |,S...S...T...T..|
00000410  4a 55 08 00 68 56 08 00  7b 57 08 00 5a 58 08 00  |JU..hV..{W..ZX..|
00000420  19 59 08 00 1c 5a 08 00  13 5b 08 00 91 5b 08 00  |.Y...Z...[...[..|
00000430  f8 5b 08 00 7c 5c 08 00  5d 5d 08 00 2a 5e 08 00  |.[..|\..]]..*^..|
00000440  8d 5e 08 00 41 5f 08 00  ef 5f 08 00 ab 60 08 00  |.^..A_..._...`..|
00000450  2f 61 08 00 ba 61 08 00  54 62 08 00 4a 63 08 00  |/a...a..Tb..Jc..|
00000460  2c 64 08 00 8d 64 08 00  58 65 08 00 dc 65 08 00  |,d...d..Xe...e..|
00000470  5c 66 08 00 dc 66 08 00  43 67 08 00 eb 67 08 00  |\f...f..Cg...g..|
00000480  71 68 08 00 f5 68 08 00  9a 69 08 00 5a 6a 08 00  |qh...h...i..Zj..|
00000490  1a 6b 08 00 e5 6c 08 00  3d 76 08 00 42 77 08 00  |.k...l..=v..Bw..|
000004a0  c5 77 08 00 8e 78 08 00  39 79 08 00 15 7a 08 00  |.w...x..9y...z..|
000004b0  f4 7a 08 00 06 7c 08 00  95 7c 08 00 63 7d 08 00  |.z...|...|..c}..|
000004c0  03 7e 08 00 b9 7e 08 00  73 7f 08 00 4b 80 08 00  |.~...~..s...K...|
000004d0  cf 80 08 00 8a 81 08 00  13 82 08 00 a0 82 08 00  |................|
000004e0  6f 83 08 00 1b 84 08 00  ce 84 08 00 9d 85 08 00  |o...............|
000004f0  2a 86 08 00 ee 86 08 00  7f 88 08 00 84 89 08 00  |*...............|
00000500  54 8a 08 00 22 8b 08 00  34 8c 08 00 47 8d 08 00  |T..."...4...G...|
00000510  f7 8d 08 00 7d 8e 08 00  03 8f 08 00 89 8f 08 00  |....}...........|
00000520  0f 90 08 00 95 90 08 00  1b 91 08 00 a0 91 08 00  |................|
00000530  25 92 08 00 aa 92 08 00  2f 93 08 00 b4 93 08 00  |%......./.......|
00000540  39 94 08 00 be 94 08 00  4d 95 08 00 52 96 08 00  |9.......M...R...|
00000550  02 97 08 00 16 98 08 00  b1 99 08 00 35 9a 08 00  |............5...|
00000560  ca 9a 08 00 56 9b 08 00  c2 9c 08 00 dc 9d 08 00  |....V...........|
00000570  8b 9e 08 00 95 9f 08 00  4e a1 08 00 7d a2 08 00  |........N...}...|
00000580  66 a3 08 00 61 a4 08 00  fe a4 08 00 93 a5 08 00  |f...a...........|
00000590  2e a6 08 00 f3 a6 08 00  bb a7 08 00 83 a8 08 00  |................|
000005a0  4b a9 08 00 13 aa 08 00  db aa 08 00 a3 ab 08 00  |K...............|
000005b0  8a ac 08 00 6a ad 08 00  3e ae 08 00 f6 ae 08 00  |....j...>.......|
000005c0  b0 b0 08 00 ab b1 08 00  94 b2 08 00 bb b3 08 00  |................|
000005d0  2a b5 08 00 bf b5 08 00  40 b6 08 00 2f b7 08 00  |*.......@.../...|
000005e0  47 b8 08 00 5f b9 08 00  3c ba 08 00 b7 bb 08 00  |G..._...<.......|
000005f0  a9 bc 08 00 d3 bd 08 00  eb be 08 00 f0 bf 08 00  |................|
00000600  b9 c0 08 00 59 c1 08 00  4b c2 08 00 08 c3 08 00  |....Y...K.......|
00000610  d5 c3 08 00 d6 c4 08 00  36 c6 08 00 86 c7 08 00  |........6.......|
00000620  66 c8 08 00 65 c9 08 00  e3 ca 08 00 d9 cb 08 00  |f...e...........|
00000630  b0 cc 08 00 d0 cd 08 00  6b cf 08 00 4f d0 08 00  |........k...O...|
00000640  33 d1 08 00 0e d2 08 00  2c d5 08 00 72 da 08 00  |3.......,...r...|
00000650  69 db 08 00 88 dd 08 00  99 df 08 00 83 e0 08 00  |i...............|
00000660  3c e3 08 00 c7 e4 08 00  5f e6 08 00 2b e7 08 00  |<......._...+...|
00000670  e6 e8 08 00 9a ea 08 00  40 eb 08 00 e3 ed 08 00  |........@.......|
00000680  59 f5 08 00 85 f6 08 00  bd f7 08 00 ac f8 08 00  |Y...............|
00000690  86 fa 08 00 f4 fb 08 00  83 fd 08 00 9e ff 08 00  |................|
000006a0  0d 01 09 00 e8 01 09 00  9e 03 09 00 50 06 09 00  |............P...|
000006b0  ff 08 09 00 a3 0b 09 00  40 12 09 00 66 14 09 00  |........@...f...|
000006c0  89 15 09 00 1e 17 09 00  76 19 09 00 1f 1b 09 00  |........v.......|
000006d0  ab 1c 09 00 99 1e 09 00  32 20 09 00 77 22 09 00  |........2 ..w"..|
000006e0  e7 25 09 00 a2 27 09 00  46 2a 09 00 8f 36 09 00  |.%...'..F*...6..|
000006f0  d2 38 09 00 65 40 09 00  20 43 09 00 35 46 09 00  |.8..e@.. C..5F..|
00000700  5f 4d 09 00 5f 5b 09 00  46 61 09 00 00 68 09 00  |_M.._[..Fa...h..|
00000710  06 6b 09 00 d6 7e 09 00  e5 9f 09 00 e7 9f 0a 00  |.k...~..........|
00000720  72 b7 0a 00 b5 e4 0a 00  7b eb 0a 00 7e eb 0a 00  |r.......{...~...|
00000730  81 eb 0a 00 85 eb 0a 00  8b eb 0a 00 b2 eb 0a 00  |................|
00000740  b8 eb 0a 00 bd eb 0a 00  cb eb 0a 00 d2 eb 0a 00  |................|
00000750  de eb 0a 00 f9 eb 0a 00  0e ec 0a 00 18 ec 0a 00  |................|
00000760  33 ec 0a 00 4b ec 0a 00  60 ec 0a 00 79 ec 0a 00  |3...K...`...y...|
00000770  8b ec 0a 00 d2 ec 0a 00  1d ed 0a 00 2c ed 0a 00  |............,...|
00000780  49 ed 0a 00 5e ed 0a 00  71 ed 0a 00 95 ed 0a 00  |I...^...q.......|
00000790  9d ed 0a 00 b7 ed 0a 00  c3 ed 0a 00 da ed 0a 00  |................|
000007a0  f0 ed 0a 00 f9 ed 0a 00  02 ee 0a 00 0a ee 0a 00  |................|
000007b0  22 ee 0a 00 2f ee 0a 00  3c ee 0a 00 49 ee 0a 00  |".../...<...I...|
000007c0  5e ee 0a 00 6b ee 0a 00  7c ee 0a 00 86 ee 0a 00  |^...k...|.......|
000007d0  91 ee 0a 00 a1 ee 0a 00  ae ee 0a 00 b7 ee 0a 00  |................|
000007e0  bf ee 0a 00 ce ee 0a 00  d6 ee 0a 00 e1 ee 0a 00  |................|
000007f0  e7 ee 0a 00 f5 ee 0a 00  fd ee 0a 00 0c ef 0a 00  |................|
00000800  17 ef 0a 00 21 ef 0a 00  29 ef 0a 00 3a ef 0a 00  |....!...)...:...|
00000810  53 ef 0a 00 5f ef 0a 00  6a ef 0a 00 7d ef 0a 00  |S..._...j...}...|
00000820  87 ef 0a 00 90 ef 0a 00  9e ef 0a 00 b4 ef 0a 00  |................|
00000830  bb ef 0a 00 c6 ef 0a 00  d2 ef 0a 00 d9 ef 0a 00  |................|
00000840  e8 ef 0a 00 f5 ef 0a 00  fc ef 0a 00 0b f0 0a 00  |................|
00000850  17 f0 0a 00 27 f0 0a 00  2a f0 0a 00 2e f0 0a 00  |....'...*.......|
00000860  32 f0 0a 00 37 f0 0a 00  3c f0 0a 00 41 f0 0a 00  |2...7...<...A...|
00000870  46 f0 0a 00 4b f0 0a 00  67 f0 0a 00 79 f0 0a 00  |F...K...g...y...|
00000880  90 f0 0a 00 a4 f0 0a 00  bd f0 0a 00 d2 f0 0a 00  |................|
00000890  ec f0 0a 00 02 f1 0a 00  17 f1 0a 00 2e f1 0a 00  |................|
000008a0  42 f1 0a 00 58 f1 0a 00  6d f1 0a 00 83 f1 0a 00  |B...X...m.......|
000008b0  9c f1 0a 00 ba f1 0a 00  d4 f1 0a 00 ee f1 0a 00  |................|

dexdump

~/.android-sdk/build-tools/23.0.1/dexdump -d \
      ./target/android/dex/classes.dex \
      > ./target/android/dex/classes.dex.dump

Processing './target/android/dex/classes.dex'...
Opened './target/android/dex/classes.dex', DEX version '035'
Class #0            -
  Class descriptor  : 'L_00_helloworld/HelloWorldKt;'
  Access flags      : 0x0011 (PUBLIC FINAL)
  Superclass        : 'Ljava/lang/Object;'
  Interfaces        -
  Static fields     -
  Instance fields   -
  Direct methods    -
    #0              : (in L_00_helloworld/HelloWorldKt;)
      name          : 'main'
      type          : '([Ljava/lang/String;)V'
      access        : 0x0019 (PUBLIC STATIC FINAL)
      code          -
      registers     : 2
      ins           : 1
      outs          : 2
      insns size    : 13 16-bit code units
020494:                                        |[020494] _00_helloworld.HelloWorldKt.main:([Ljava/lang/String;)V
0204a4: 1a00 1310                              |0000: const-string v0, "args" // string@1013
0204a8: 7120 a811 0100                         |0002: invoke-static {v1, v0}, Lkotlin/jvm/internal/Intrinsics;.checkParameterIsNotNull:(Ljava/lang/Object;Ljava/lang/String;)V // method@11a8
0204ae: 1a01 0808                              |0005: const-string v1, "Hello Devoxx" // string@0808
0204b2: 6200 0c00                              |0007: sget-object v0, Ljava/lang/System;.out:Ljava/io/PrintStream; // field@000c
0204b6: 6e20 3f00 1000                         |0009: invoke-virtual {v0, v1}, Ljava/io/PrintStream;.println:(Ljava/lang/Object;)V // method@003f
0204bc: 0e00                                   |000c: return-void
      catches       : (none)
      positions     : 
        0x0007 line=4
      locals        : 

  Virtual methods   -
  source_file_idx   : 2057 (HelloWorld.kt)
...

smali

sh ./scripts/lib/dextools/d2j-dex2smali.sh \
     ./target/android/dex/classes.dex -f \
     -o ./target/android/smali

.class public final L_00_helloworld/HelloWorldKt;
.super Ljava/lang/Object;
.source "HelloWorld.kt"

.annotation system Ldalvik/annotation/SourceDebugExtension;
  value = "SMAP\nHelloWorld.kt\nKotlin\n*S Kotlin\n*F\n+ 1 HelloWorld.kt\n_00_helloworld/HelloWorldKt\n*L\n1#1,5:1\n*E\n"
.end annotation
.annotation runtime Lkotlin/Metadata;
  bv = {
    1,
    0,
    2
  }
  d1 = {
    "\u0000\u0012\n\u0000\n\u0002\u0010\u0002\n\u0000\n\u0002\u0010\u0011\n\u0002\u0010\u000e\n\u0000\u001a\u0019\u0010\u0000\u001a\u00020\u00012\u000c\u0010\u0002\u001a\u0008\u0012\u0004\u0012\u00020\u00040\u0003\u00a2\u0006\u0002\u0010\u0005"
  }
  d2 = {
    "main",
    "",
    "args",
    "",
    "",
    "([Ljava/lang/String;)V"
  }
  k = 2
  mv = {
    1,
    1,
    9
  }
.end annotation

.method public final static main([Ljava/lang/String;)V
  .parameter # [Ljava/lang/String;
    .annotation build Lorg/jetbrains/annotations/NotNull;
    .end annotation
  .end parameter
  .registers 2
    const-string v0, "args"
    invoke-static { p0, v0 }, Lkotlin/jvm/internal/Intrinsics;->checkParameterIsNotNull(Ljava/lang/Object;Ljava/lang/String;)V
    const-string p0, "Hello Devoxx"
  .line 4
    sget-object v0, Ljava/lang/System;->out:Ljava/io/PrintStream;
    invoke-virtual { v0, p0 }, Ljava/io/PrintStream;->println(Ljava/lang/Object;)V
    return-void
.end method

Autres structures

if-then-else.kt

fun handleAstronomicalBody(body: AstronomicalBody) {
    val message =
        if (body is Planet && body.name == "Earth") {
            "Welcome Earth"
        } else {
            "Welcome martian"
        }
    println(message)
}

for.kt

fun main(args: Array<String>) {
    for (body in SolarSystem.bodies) { // 🤢
        print(body)
    }
}

for.java

package _09_structures;

import astronomy.AstronomicalBody;
import astronomy.SolarSystem;
import java.util.Iterator;
import kotlin.Metadata;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 2,
   d1 = {"\u0000\u0012\n\u0000\n\u0002\u0010\u0002\n\u0000\n\u0002\u0010\u0011\n\u0002\u0010\u000e\n\u0000\u001a\u0019\u0010\u0000\u001a\u00020\u00012\f\u0010\u0002\u001a\b\u0012\u0004\u0012\u00020\u00040\u0003¢\u0006\u0002\u0010\u0005"},
   d2 = {"main", "", "args", "", "", "([Ljava/lang/String;)V"}
)
public final class ForKt {
   public static final void main(@NotNull String[] args) {
      Intrinsics.checkParameterIsNotNull(args, "args");
      Iterator var2 = SolarSystem.INSTANCE.getBodies().iterator();

      while(var2.hasNext()) {
         AstronomicalBody body = (AstronomicalBody)var2.next();
         System.out.print(body);
      }

   }
}

ByteCode du for

Compiled from "for.kt"
public final class _09_structures.ForKt {
  public static final void main(java.lang.String[]);
    Code:
       0: aload_0
       1: ldc           #9                  // String args
       3: invokestatic  #15                 // Method kotlin/jvm/internal/Intrinsics.checkParameterIsNotNull:(Ljava/lang/Object;Ljava/lang/String;)V
       6: getstatic     #21                 // Field astronomy/SolarSystem.INSTANCE:Lastronomy/SolarSystem;
       9: invokevirtual #25                 // Method astronomy/SolarSystem.getBodies:()Ljava/util/Collection;
      12: invokeinterface #31,  1           // InterfaceMethod java/util/Collection.iterator:()Ljava/util/Iterator;
      17: astore_2
      18: aload_2
      19: invokeinterface #37,  1           // InterfaceMethod java/util/Iterator.hasNext:()Z
      24: ifeq          47
      27: aload_2
      28: invokeinterface #41,  1           // InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object;
      33: checkcast     #43                 // class astronomy/AstronomicalBody
      36: astore_1
      37: getstatic     #49                 // Field java/lang/System.out:Ljava/io/PrintStream;
      40: aload_1
      41: invokevirtual #55                 // Method java/io/PrintStream.print:(Ljava/lang/Object;)V
      44: goto          18
      47: return
}

while-do.kt

while (x > 0) {
    x--
}

do {
    val y = retrieveData()
} while (y != null) // y is visible here!

when.kt

for (body in SolarSystem.bodies) { // 🤢

    val message = when (body) {
        is Planet -> "Planet ${body.name}"
        is Star   -> "Star ${body.name}"
        else      -> null
    }

    if (message != null) {
        println(message)
    }
}

for-factorial.kt

// Note: assert(n >= 0)
fun forFactorial(n: Int): Int { // 🤢
    var acc = 1
    for (i in 1..n) {
        acc *= i
    }
    return acc
}

ByteCode factoriel avec for

Compiled from "for-factorial.kt"
public final class _09_structures.recusion.For_factorialKt {
  public static final int forFactorial(int);
    Code:
       0: iconst_1
       1: istore_1
       2: iconst_1
       3: istore_2
       4: iload_0
       5: istore_3
       6: iload_2
       7: iload_3
       8: if_icmpgt     26
      11: iload_1
      12: iload_2
      13: imul
      14: istore_1
      15: iload_2
      16: iload_3
      17: if_icmpeq     26
      20: iinc          2, 1
      23: goto          11
      26: iload_1
      27: ireturn
}

rec-factorial.kt

// Note: assert(n >= 0)
fun recFactorial(n: Int): Int =
    if (n < 1) 1 else n * recFactorial(n - 1)

ByteCode factoriel avec recursivité

Compiled from "rec-factorial.kt"
public final class _09_structures.recusion.Rec_factorialKt {
  public static final int recFactorial(int);
    Code:
       0: iload_0
       1: iconst_1
       2: if_icmpge     9
       5: iconst_1
       6: goto          17
       9: iload_0
      10: iload_0
      11: iconst_1
      12: isub
      13: invokestatic  #8                  // Method recFactorial:(I)I
      16: imul
      17: ireturn
}

tailrec-factorial.kt

// Note: assert(n >= 0)
fun tailRecFactorial(n: Int): Int {

    tailrec fun aux(n: Int, acc: Int): Int =
        if (n < 1) acc else aux(n - 1, acc * n)

    return aux(n, 1)
}

ByteCode factoriel avec recursivité terminal 1/2

Compiled from "tailrec-factorial.kt"
public final class _09_structures.recusion.Tailrec_factorialKt {
  public static final int tailRecFactorial(int);
    Code:
       0: getstatic     #12                 // Field _09_structures/recusion/Tailrec_factorialKt$tailRecFactorial$1.INSTANCE:L_09_structures/recusion/Tailrec_factorialKt$tailRecFactorial$1;
       3: astore_1
       4: aload_1
       5: iload_0
       6: iconst_1
       7: invokevirtual #16                 // Method _09_structures/recusion/Tailrec_factorialKt$tailRecFactorial$1.invoke:(II)I
      10: ireturn
}

ByteCode factoriel avec recursivité terminal 2/2

Compiled from "tailrec-factorial.kt"
final class _09_structures.recusion.Tailrec_factorialKt$tailRecFactorial$1 extends kotlin.jvm.internal.Lambda implements kotlin.jvm.functions.Function2<java.lang.Integer, java.lang.Integer, java.lang.Integer> {
  public static final _09_structures.recusion.Tailrec_factorialKt$tailRecFactorial$1 INSTANCE;

  public java.lang.Object invoke(java.lang.Object, java.lang.Object);
    Code:
       0: aload_0
       1: aload_1
       2: checkcast     #11                 // class java/lang/Number
       5: invokevirtual #15                 // Method java/lang/Number.intValue:()I
       8: aload_2
       9: checkcast     #11                 // class java/lang/Number
      12: invokevirtual #15                 // Method java/lang/Number.intValue:()I
      15: invokevirtual #18                 // Method invoke:(II)I
      18: invokestatic  #24                 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
      21: areturn

  public final int invoke(int, int);
    Code:
       0: iload_1
       1: iconst_1
       2: if_icmpge     9
       5: iconst_1
       6: goto          25
       9: aload_0
      10: checkcast     #2                  // class _09_structures/recusion/Tailrec_factorialKt$tailRecFactorial$1
      13: pop
      14: iload_1
      15: iconst_1
      16: isub
      17: iload_2
      18: iload_1
      19: imul
      20: istore_2
      21: istore_1
      22: goto          0
      25: ireturn

  _09_structures.recusion.Tailrec_factorialKt$tailRecFactorial$1();
    Code:
       0: aload_0
       1: iconst_2
       2: invokespecial #34                 // Method kotlin/jvm/internal/Lambda."<init>":(I)V
       5: return

  static {};
    Code:
       0: new           #2                  // class _09_structures/recusion/Tailrec_factorialKt$tailRecFactorial$1
       3: dup
       4: invokespecial #57                 // Method "<init>":()V
       7: putstatic     #59                 // Field INSTANCE:L_09_structures/recusion/Tailrec_factorialKt$tailRecFactorial$1;
      10: return
}

Performances sur `10!` 1/2

Ne croyez pas les benchmarks, faites les vous-même !

https://github.com/MonkeyPatchIo/kotlin-perf

Benchmark	Mode	Cnt	Score	Error	Units
factorialJavaFor	thrpt	200	433372258.508	± 1218796.228	ops/s
factorialKotlinFor	thrpt	200	374900724.013	± 1836466.839	ops/s
factorialJavaRec	thrpt	200	71945600.003	± 1621282.609	ops/s
factorialKotlinRec	thrpt	200	75889169.327	± 803516.130	ops/s
factorialJavaTailRec	thrpt	200	74708348.540	± 385285.112	ops/s
factorialKotlinTailRec	thrpt	200	432005903.950	± 2558012.821	ops/s
factorialJavaReduce	thrpt	200	21560855.907	± 586144.742	ops/s
factorialKotlinReduce	thrpt	200	99169022.775	± 2711794.007	ops/s

Performances sur `10!` 2/2

Bilan structures

Il y a aussi des break et continue, label pour les boucles
when peut être utiliser avec
- des constantes,
- plusieurs valeurs séparées par ,
- une expression
- avec is et un type (avec un 'smart cast')

✨ Tips

privilégier les when si vous avez plus de 2 cas
si vous faites des fonctions récursives, faites les tailrec

Extensions de fonctions

extension.kt

val AstronomicalBody.size: Int
    get() = name.length

fun AstronomicalBody.display() = "Body $name $size"

fun main(args: Array<String>) {
    SolarSystem.bodies
        .forEach { println(it.display()) }
}

extension.java

package _08_extension;

import astronomy.AstronomicalBody;
import astronomy.SolarSystem;
import java.util.Iterator;
import kotlin.Metadata;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;

@Metadata(
        mv = {1, 1, 9},
        bv = {1, 0, 2},
        k = 2,
        d1 = {"\u0000 \n\u0000\n\u0002\u0010\b\n\u0002\u0018\u0002\n\u0002\b\u0003\n\u0002\u0010\u0002\n\u0000\n\u0002\u0010\u0011\n\u0002\u0010\u000e\n\u0002\b\u0002\u001a\u0019\u0010\u0005\u001a\u00020\u00062\f\u0010\u0007\u001a\b\u0012\u0004\u0012\u00020\t0\b¢\u0006\u0002\u0010\n\u001a\n\u0010\u000b\u001a\u00020\t*\u00020\u0002\"\u0015\u0010\u0000\u001a\u00020\u0001*\u00020\u00028F¢\u0006\u0006\u001a\u0004\b\u0003\u0010\u0004"},
        d2 = {"size", "", "Lastronomy/AstronomicalBody;", "getSize", "(Lastronomy/AstronomicalBody;)I", "main", "", "args", "", "", "([Ljava/lang/String;)V", "display"}
)
public final class ExtensionKt {
   public static final int getSize(@NotNull AstronomicalBody $receiver) {
      Intrinsics.checkParameterIsNotNull($receiver, "$receiver");
      return $receiver.getName().length();
   }

   @NotNull
   public static final String display(@NotNull AstronomicalBody $receiver) {
      Intrinsics.checkParameterIsNotNull($receiver, "$receiver");
      return "Body " + $receiver.getName() + ' ' + getSize($receiver);
   }

   public static final void main(@NotNull String[] args) {
      Intrinsics.checkParameterIsNotNull(args, "args");
      Iterable $receiver$iv = (Iterable)SolarSystem.INSTANCE.getBodies();
      Iterator var2 = $receiver$iv.iterator();

      while(var2.hasNext()) {
         Object element$iv = var2.next();
         AstronomicalBody it = (AstronomicalBody)element$iv;
         String var5 = display(it);
         System.out.println(var5);
      }

   }
}

Extension

Permet d'enrichir les APIs Java
- Spring
- RxKotlin
- SparkJava
- ...
Permet la SoC (Separation of Concerns)

Les collections

Collections

Les Maps

api.kt

val s = SolarSystem.bodies
    .filterIsInstance<Planet>()
    .flatMap { planet -> planet.moons } // 😻
    .filterNot { it.name.startsWith("S/") }
    .sortedBy { it.name }
//        .fold("") { acc, moon ->
//            (if (acc == "") "" else "$acc,\n") + moon.name
//        }
    .joinToString(",\n") { it.name }

println(s)

immutable-mutable.kt

fun main(args: Array<String>) {

    val earthMoon = listOf(Moon("moon"))
    val add = earthMoon + Moon("moon 2")

    println("earthMoon: $earthMoon") // earthMoon: [Moon(name=moon)]
    println("add: $add")             // add: [Moon(name=moon), Moon(name=moon 2)]
    println("reference equality: ${earthMoon === add}") //reference equality: false

    println("\n")
    val earthMoon2 = mutableListOf(Moon("moon"))
    val add2 = earthMoon2.add(Moon("moon 2"))

    println("earthMoon2: $earthMoon2") // earthMoon2: [Moon(name=moon), Moon(name=moon 2)]
    println("add2: $add2")             // add2: true
}

break-immutable.kt

fun main(args: Array<String>) {
    val moons = (1..9).map { Moon("Moon #$it") }.toList()

    println(moons.javaClass) // class java.util.ArrayList

    moons.javaClass.methods
        .find { it.name == "add" && it.parameterCount == 1 }
        ?.invoke(moons, Moon("XXX"))

    println(moons.joinToString("\n"))
    // Moon(name=Moon #1)
    // Moon(name=Moon #2)
    // Moon(name=Moon #3)
    // Moon(name=Moon #4)
    // Moon(name=Moon #5)
    // Moon(name=Moon #6)
    // Moon(name=Moon #7)
    // Moon(name=Moon #8)
    // Moon(name=Moon #9)
    // Moon(name=XXX)
}

sequence.kt

val s = SolarSystem.bodies.asSequence()
    .filterIsInstance<Planet>()
    .flatMap { planet -> planet.moons.asSequence() } // 😻
    .filterNot { it.name.startsWith("S/") }
    .sortedBy { it.name }
    .joinToString(",\n") { it.name }

println(s)

Performance des sequences 1/2

Ne croyez pas les benchmarks, faites les vous-même !

https://github.com/MonkeyPatchIo/kotlin-perf

Benchmark	Mode	Cnt	Score	Error	Units
collectionApiClassic	thrpt	200	44535.029	± 3550.944	ops/s
collectionApiSequence	thrpt	200	23652.238	± 1967.535	ops/s

sequence2.kt

val s = SolarSystem.bodies.asSequence()
    .filterIsInstance<Planet>()
    .flatMap { planet -> planet.moons.asSequence() } // 😻
    .filterNot { it.name.startsWith("S/") }
    .map { it.name }
    .first()

println(s)

Performance des sequences 2/2

Ne croyez pas les benchmarks, faites les vous-même !

https://github.com/MonkeyPatchIo/kotlin-perf

Benchmark	Mode	Cnt	Score	Error	Units
collectionApiClassicFirst	thrpt	200	241752.062	± 5022.663	ops/s
collectionApiSequenceFirst	thrpt	200	3615451.391	± 454502.198	ops/s

timed-sequence.kt

fun <T> timed(block: () -> T) {
    val startTime = System.currentTimeMillis()
    val result = block()
    val endTime = System.currentTimeMillis()
    val duration = endTime - startTime
    val readable = String.format("%d min %02d seconds", duration / 60000, (duration % 60000) / 1000)
    println("$result in $readable")
}

fun main(args: Array<String>) {
    fun Long.toMB(): String =
        "${this / 1048576}MB"

    fun Runtime.usedMemory(): String =
        (totalMemory() - freeMemory()).toMB()

    fun Runtime.getMemoryInfo(): String =
        "used: ${usedMemory()}, total: ${totalMemory().toMB()}"

    timed {
        (0..1_000_000)
            .asSequence()
            .onEach {
                if (it % 10_000 == 0) {
                    println(Runtime.getRuntime().getMemoryInfo())
                }
                println(it)
            }
            .map { Moon(it.toString()) }
            .first()
    }
}

ranges.kt

for (i in 1..3) print(i) // prints 123

for (i in 3 downTo 1) print(i) // prints 321

for (i in 1..5 step 2) print(i) // prints 135

ranges.java

package _11_collections_2;

import kotlin.Metadata;
import kotlin.jvm.internal.Intrinsics;
import kotlin.ranges.IntProgression;
import kotlin.ranges.IntRange;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 2,
   d1 = {"\u0000\u0012\n\u0000\n\u0002\u0010\u0002\n\u0000\n\u0002\u0010\u0011\n\u0002\u0010\u000e\n\u0000\u001a\u0019\u0010\u0000\u001a\u00020\u00012\f\u0010\u0002\u001a\b\u0012\u0004\u0012\u00020\u00040\u0003¢\u0006\u0002\u0010\u0005"},
   d2 = {"main", "", "args", "", "", "([Ljava/lang/String;)V"}
)
public final class RangesKt {
   public static final void main(@NotNull String[] args) {
      Intrinsics.checkParameterIsNotNull(args, "args");
      int i = 1;

      byte var2;
      for(var2 = 3; i <= var2; ++i) {
         System.out.print(i);
      }

      i = 3;

      for(var2 = 1; i >= var2; --i) {
         System.out.print(i);
      }

      byte var4 = 1;
      IntProgression var10000 = kotlin.ranges.RangesKt.step((IntProgression)(new IntRange(var4, 5)), 2);
      i = var10000.getFirst();
      int var5 = var10000.getLast();
      int var3 = var10000.getStep();
      if (var3 > 0) {
         if (i > var5) {
            return;
         }
      } else if (i < var5) {
         return;
      }

      while(true) {
         System.out.print(i);
         if (i == var5) {
            return;
         }

         i += var3;
      }
   }
}

tuples.kt

fun main(args: Array<String>) {
    val aPair = "Earth" to "Moon" // ~  Pair("Earth", "Moon")
    val (planet, moon) = aPair

    val aTriple = Triple("Voyager 1", 1977, listOf("Jupiter", "Saturn"))
    val (probeNane, launchYear, flyOver) = aTriple
}

tuples.java

package _11_collections_2;

import java.util.List;
import kotlin.Metadata;
import kotlin.Pair;
import kotlin.Triple;
import kotlin.collections.CollectionsKt;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;

@Metadata(
        mv = {1, 1, 9},
        bv = {1, 0, 2},
        k = 2,
        d1 = {"\u0000\u0012\n\u0000\n\u0002\u0010\u0002\n\u0000\n\u0002\u0010\u0011\n\u0002\u0010\u000e\n\u0000\u001a\u0019\u0010\u0000\u001a\u00020\u00012\f\u0010\u0002\u001a\b\u0012\u0004\u0012\u00020\u00040\u0003¢\u0006\u0002\u0010\u0005"},
        d2 = {"main", "", "args", "", "", "([Ljava/lang/String;)V"}
)
public final class TuplesKt {
   public static final void main(@NotNull String[] args) {
      Intrinsics.checkParameterIsNotNull(args, "args");
      Pair aPair = kotlin.TuplesKt.to("Earth", "Moon");
      String var2 = (String)aPair.component1();
      String moon = (String)aPair.component2();
      Triple aTriple = new Triple("Voyager 1", 1977, CollectionsKt.listOf(new String[]{"Jupiter", "Saturn"}));
      String var5 = (String)aTriple.component1();
      int var6 = ((Number)aTriple.component2()).intValue();
      List flyOver = (List)aTriple.component3();
   }
}

Bilan collection

💪 Super on a de l'immutabilité, des map, flatMap, fold, aggregate,...
🤨 Mais ça reste des collections Java
⚖️ Avant d'utiliser les Sequence, faites des mesures

Les delegates

delegate.kt

import kotlin.properties.ReadOnlyProperty
import kotlin.reflect.KProperty

fun main(args: Array<String>) {
    val value: String by MyDelegateClass()
    println(value)
}

class MyDelegateClass : ReadOnlyProperty<Nothing?, String> {
    override operator fun getValue(thisRef: Nothing?,
                                   property: KProperty<*>) = "Hello Devoxx"
}

lazy.kt

object DeepThought {
    fun answer(): Int {
        print("Computing ...")
        return 42
    }
}

fun main(args: Array<String>) {

    val ultimateQuestionOfLife: Int by lazy {
        DeepThought.answer()
    }
    println("The Ultimate Question of Life, " +
                    "the Universe and Everything ?")
    print("Answer: ")
    println(ultimateQuestionOfLife)
}

observable.kt

import kotlin.properties.Delegates

fun main(args: Array<String>) {

    var observable: String by Delegates.observable("Initial value") {
        _, old, new ->
            println("$old -> $new")
    }

    observable = "new value"
}

lateinit.kt

lateinit var str: String

fun main(args: Array<String>) {
    // println(str) kotlin.UninitializedPropertyAccessException
    str = "Hello Devoxx"
    println(str)
}

Delegate

Lazy : utile pour les propriétés qui ne sont pas systématiquement utilisées.
⚠️ À manipuler avec précaution dans les activités Android ( avec le cycle de vie, cela peut référencer une ancienne instance)
Delegate : Observable, Not null, ...
lateinit : évite les null check pour les propriétés qui ne peuvent être initialisées immédiatement (ex référence de vues sur Activity, Fragment).
- Ne peut pas être utilisé avec les types primitifs

Un peu plus sur les fonctions

inline.kt

import java.time.Instant

class Logger(private val name: String) {
    private enum class Level { TRACE, DEBUG, INFO, WARN, ERROR, FATAL }
    private val level = Level.INFO

    fun info(message: () -> String) {
        log(Level.INFO, message)
    }

    private inline fun log(lvl: Level, message: () -> String) { // inline
        if (level >= lvl) {
            println("[${level.name}] $name - ${message()}")
        }
    }
}

fun main(args: Array<String>) {
    val logger = Logger("Main")

    logger.info { "Time: ${Instant.now()}" }
}

Logger.java

package _13_advanced_function;

import kotlin.Metadata;
import kotlin.jvm.functions.Function0;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {1, 1, 9},
   bv = {1, 0, 2},
   k = 1,
   d1 = {"\u0000&\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0000\n\u0002\u0010\u000e\n\u0002\b\u0002\n\u0002\u0018\u0002\n\u0000\n\u0002\u0010\u0002\n\u0000\n\u0002\u0018\u0002\n\u0002\b\u0003\u0018\u00002\u00020\u0001:\u0001\rB\r\u0012\u0006\u0010\u0002\u001a\u00020\u0003¢\u0006\u0002\u0010\u0004J\u0014\u0010\u0007\u001a\u00020\b2\f\u0010\t\u001a\b\u0012\u0004\u0012\u00020\u00030\nJ\u001f\u0010\u000b\u001a\u00020\b2\u0006\u0010\f\u001a\u00020\u00062\f\u0010\t\u001a\b\u0012\u0004\u0012\u00020\u00030\nH\u0082\bR\u000e\u0010\u0005\u001a\u00020\u0006X\u0082\u0004¢\u0006\u0002\n\u0000R\u000e\u0010\u0002\u001a\u00020\u0003X\u0082\u0004¢\u0006\u0002\n\u0000"},
   d2 = {"L_13_advanced_function/Logger;", "", "name", "", "(Ljava/lang/String;)V", "level", "L_13_advanced_function/Logger$Level;", "info", "", "message", "Lkotlin/Function0;", "log", "lvl", "Level"}
)
public final class Logger {
   private final Logger.Level level;
   private final String name;

   public final void info(@NotNull Function0 message) {
      Intrinsics.checkParameterIsNotNull(message, "message");
      Logger.Level lvl$iv = Logger.Level.INFO;
      if (access$getLevel$p(this).compareTo((Enum)lvl$iv) >= 0) {
         String var4 = '[' + access$getLevel$p(this).name() + "] " + access$getName$p(this) + " - " + (String)message.invoke();
         System.out.println(var4);
      }

   }

   private final void log(Logger.Level lvl, Function0 message) {
      if (access$getLevel$p(this).compareTo((Enum)lvl) >= 0) {
         String var4 = '[' + access$getLevel$p(this).name() + "] " + access$getName$p(this) + " - " + (String)message.invoke();
         System.out.println(var4);
      }

   }

   public Logger(@NotNull String name) {
      Intrinsics.checkParameterIsNotNull(name, "name");
      super();
      this.name = name;
      this.level = Logger.Level.INFO;
   }

   // $FF: synthetic method
   @NotNull
   public static final Logger.Level access$getLevel$p(Logger $this) {
      return $this.level;
   }

   // $FF: synthetic method
   @NotNull
   public static final String access$getName$p(Logger $this) {
      return $this.name;
   }

   @Metadata(
      mv = {1, 1, 9},
      bv = {1, 0, 2},
      k = 1,
      d1 = {"\u0000\f\n\u0002\u0018\u0002\n\u0002\u0010\u0010\n\u0002\b\u0007\b\u0082\u0001\u0018\u00002\b\u0012\u0004\u0012\u00020\u00000\u0001B\u0007\b\u0002¢\u0006\u0002\u0010\u0002j\u0002\b\u0003j\u0002\b\u0004j\u0002\b\u0005j\u0002\b\u0006j\u0002\b\u0007j\u0002\b\b"},
      d2 = {"L_13_advanced_function/Logger$Level;", "", "(Ljava/lang/String;I)V", "TRACE", "DEBUG", "INFO", "WARN", "ERROR", "FATAL"}
   )
   private static enum Level {
      TRACE,
      DEBUG,
      INFO,
      WARN,
      ERROR,
      FATAL;

      protected Level() {
      }
   }
}

reified.kt

class Pojo {
    var name: String? = null
    override fun toString() = "Pojo $name"
}

object JavaBeanBuilder {

    fun <T> createBean(clazz: Class<T>): T =
        clazz.newInstance()

    inline fun <reified T> createBean(): T =
        createBean(T::class.java)
}

fun main(args: Array<String>) {
    val p1 = Pojo()
    p1.name = "Plop1"
    println(p1)

    val p2 = JavaBeanBuilder.createBean<Pojo>()
    p2.name = "Plop2"
    println(p2)
}

reified.java

package _13_advanced_function;

import kotlin.Metadata;
import kotlin.jvm.internal.Intrinsics;
import org.jetbrains.annotations.NotNull;

@Metadata(
        mv = {1, 1, 9},
        bv = {1, 0, 2},
        k = 2,
        d1 = {"\u0000\u0012\n\u0000\n\u0002\u0010\u0002\n\u0000\n\u0002\u0010\u0011\n\u0002\u0010\u000e\n\u0000\u001a\u0019\u0010\u0000\u001a\u00020\u00012\f\u0010\u0002\u001a\b\u0012\u0004\u0012\u00020\u00040\u0003¢\u0006\u0002\u0010\u0005"},
        d2 = {"main", "", "args", "", "", "([Ljava/lang/String;)V"}
)
public final class ReifiedKt {
    public static final void main(@NotNull String[] args) {
        Intrinsics.checkParameterIsNotNull(args, "args");
        Pojo p1 = new Pojo();
        p1.setName("Plop1");
        System.out.println(p1);
        JavaBeanBuilder this_$iv = JavaBeanBuilder.INSTANCE;
        Pojo p2 = (Pojo)this_$iv.createBean(Pojo.class);
        p2.setName("Plop2");
        System.out.println(p2);
    }
}

Plus sur les fonctions

Cas d'utilisation du `reified`

Pour créer des extensions Kotlin des fonctions Java qui utilisent des Class<T>

Cas d'utilisation des `inline`, `noinline`, `crossinline`

Quand on utilise reified
Quand on sait se qu'on fait, https://kotlinlang.org/docs/reference/inline-functions.html

Conclusion

Android

Serveur

Supporté officiellement depuis Spring 5, Spring Boot 2
SparkJava, javalin
Vert.x
KTor
...

Web et Natif

🕸 Web

Partager du code commun
Use Kotlin with npm, webpack and react

Natif

Faire des applications sans JVM
Partager du code avec iOS
WebAssembly

Bilan

💎 JVM
😎 Le byte code c'est cool
🔮 Généralement, ça ne suffit pas pour prédire les performances
⚖️ Mesurez !

Tendance

Stackoverflow insights

Kotlin vs Java

C'est déjà mature
✊ Code plus expressif, plus sûr, plus simple
🤝 Interopérable avec Java
👍 Outillage (editeur, gradle, maven)
👍 Ecosystème et communauté
🚀 Évolution rapide
🐣 Code multiplatform
DSL

Kotlin réussit une belle alchimie entre pragmatisme, puissance, sûreté, accessibilité.

Liens

Liens presentation

Slides en HTML: http://bit.ly/KotlinDevoxxFR
Slides en PDF: http://bit.ly/KotlinDevoxxFRpdf
kotlin-perf
Kotlin by example
catnip

Bibliothèques

Merci

Questions ?

Pensez au votes et aux retours

Deep Dive Kotlin : du Hello World au ByteCode

Speakers

Emmanuel Vinas

Igor Laborie

🗺 Roadmap

ByteCode Java ?

javac

HelloWorld.java

Java ByteCode binary

Explorons le ByteCode

À propos du ByteCode

Jouons un peu

Liens

Introduction Kotlin

Historique

Cibles

JVM et Android

JavaScript

Native avec LLVM

HelloWorld.kt

kotlinc

hexdump

Java ByteCode

HelloWorld-java

Bilan HelloWorld.kt

Performance HelloWorld.kt

Les bases

val-var.kt

string-template.kt

string-template.java

ByteCode de string-template

numeric.kt

numeric.java

ByteCode de numeric

C'est simple

null-safety

billion-dollar mistake

null-safety.kt

null-safety.java

Bilan null-safety

Les types

Types basiques

Types basiques nullable

todo.kt

Hierarchie des types

Les fonctions

named-params.kt

named-params.java

default-value.kt

default-value.java

ByteCode de default-value

C'est fun !

✨ Conseils

📝 Notes

Les lambdas

function.kt

function.java

lambda.kt

lambda.java

let.kt

let.java

Les lambdas

Les classes

astronomy.kt

astronomy.java

Héritage en Kotlin

Génériques

Borne supérieure

Projection *

Sealed

Alias en Kotlin

ByteCode d'alias

Classe, le bilan

Pause

ByteCode Android

Compilation pour Android

Dalvik EXecutable format

dexdump

smali

Autres structures

Deep Dive Kotlin :
du Hello World au ByteCode

C'est `fun` !

Projection `*`

Performances sur `10!` 1/2

Performances sur `10!` 2/2

Cas d'utilisation du `reified`

Cas d'utilisation des `inline`, `noinline`, `crossinline`