JVM languages shootout - Java, Scala & *Kotlin*

Java is probably the most popular statically typed language for years.
In the last decade, there has been a significant rise of other languages running on the Java Virtual Machine.
In this talk, I will compare three of the most popular JVM languages: Java, Scala, and Kotlin. We will see where each language shines and some of the advantages of each of them.
We will also take a deeper look of Kotlin - the (relatively) new kid on the block.

Transcript

1. JVM languages shootout Java, Scala & Kotlin
2. IS THERE A DOCTOR IN THE AUDIENCE?
3. IS THERE A DOCTOR JAVA DEVELOPER IN THE AUDIENCE?
5. Which one should I pick?
6. TL;DL* - pick Kotlin *Too Long; Didn’t Listen
7. • Look at trends • Kotlin vs. Java • Kotlin vs. Scala Plan B
8. Google Trends - Scala
9. Trends - Scala + Kotlin
10. Trends + Java
16. Why do developers ❤ Kotlin?
18. Boilerplate In computer programming, boilerplate code or boilerplate refers to sections of code that have to be included in many places with little or no alteration. It is often used when referring to languages that are considered verbose, i.e. the programmer must write a lot of code to do minimal jobs.
19. Boilerplate boilerplate - little or no alteration. verbose a lot of code to do minimal jobs.
20. Java vs Kotlin • Java is verbose
21. IDE
22. Hello Kotlin! Java public class Hello { public static void main(String[] args) { System.out.println("Hello!"); } } Kotlin fun main() { println("Hello!") }
23. POJO Class Java public class AdCpcData { private int adId; private double cpc; }
24. POJO Class Java public class AdCpcData { private int adId; private double cpc; public AdCpcData(final int adId, final double cpc) { this.adId = adId; this.cpc = cpc; } public double getCpc() { return cpc; } public int getAdId() { return adId; } public void setAdId(final int adId) { this.adId = adId; } public void setCpc(final double cpc) { this.cpc = cpc; } }
25. POJO Class Java public class AdCpcData { private int adId; private double cpc; public AdCpcData(final int adId, final double cpc) { this.adId = adId; this.cpc = cpc; } public double getCpc() { return cpc; } public int getAdId() { return adId; } public void setAdId(final int adId) { this.adId = adId; } public void setCpc(final double cpc) { this.cpc = cpc; } } equals(), hashcode(), toString()…
26. POJO Class Java public class AdCpcData { private int adId; private double cpc; public AdCpcData(final int adId, final double cpc) { this.adId = adId; this.cpc = cpc; } public double getCpc() { return cpc; } public int getAdId() { return adId; } public void setAdId(final int adId) { this.adId = adId; } public void setCpc(final double cpc) { this.cpc = cpc; } @Override public String toString() { return com.google.common.base.Objects.toStringHelper(this) .add("adId", adId) .add("cpc", cpc) .toString(); } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; AdCpcData adCpcData = (AdCpcData) o; return adId == adCpcData.adId && Double.compare(adCpcData.cpc, cpc) == 0; } @Override public int hashCode() { return Objects.hash(adId, cpc); } } equals(), hashcode(), toString()…
27. POJO Class Java public class AdCpcData { private int adId; private double cpc; public AdCpcData(final int adId, final double cpc) { this.adId = adId; this.cpc = cpc; } public double getCpc() { return cpc; } public int getAdId() { return adId; } public void setAdId(final int adId) { this.adId = adId; } public void setCpc(final double cpc) { this.cpc = cpc; } @Override public String toString() { return com.google.common.base.Objects.toStringHelper(this) .add("adId", adId) .add("cpc", cpc) .toString(); } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; AdCpcData adCpcData = (AdCpcData) o; return adId == adCpcData.adId && Double.compare(adCpcData.cpc, cpc) == 0; } @Override public int hashCode() { return Objects.hash(adId, cpc); } } equals(), hashcode(), toString()… 57 LOC
28. Data Class Java public class AdCpcData { private int adId; private double cpc; public AdCpcData(final int adId, final double cpc) { this.adId = adId; this.cpc = cpc; } public double getCpc() { return cpc; } public int getAdId() { return adId; } public void setAdId(final int adId) { this.adId = adId; } public void setCpc(final double cpc) { this.cpc = cpc; } @Override public String toString() { return com.google.common.base.Objects.toStringHelper(this) .add("adId", adId) .add("cpc", cpc) .toString(); } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; AdCpcData adCpcData = (AdCpcData) o; return adId == adCpcData.adId && Double.compare(adCpcData.cpc, cpc) == 0; } @Override public int hashCode() { return Objects.hash(adId, cpc); } } Kotlin data class AdCpcData( var adId: Int, var cpc: Double )
29. Variable declaration Java private final Map<String, String> myMap = new HashMap<>(); myMap.put("Hi", "There"); Kotlin val myMap = mapOf("Hi" to "There")
30. Java vs Kotlin • Many more boilerplate examples… • But Java do make some progress…
32. What’s wrong with Scala?
36. What’s wrong with Scala? • Readability sucks.
37. What’s wrong with Scala? • Readability sucks. Examples: – Collections  // Kotlin ^^^ fun <T, R> map(transform: (T) -> R): List<R>
38. What’s wrong with Scala? • Readability sucks. Examples: – Collections  def map[B, That](f: A => B) (implicit bf: CanBuildFrom[Repr, B, That]): That
39. What’s wrong with Scala? • Readability sucks. Examples: – Collections – Implicit conversions
40. What’s wrong with Scala? • Readability sucks. Examples: – Collections – Implicit conversions – Operator overloading
41. What’s wrong with Scala? • Readability sucks. Examples: – Collections – Implicit conversions – Operator overloading – Underscore 
42. What’s wrong with Scala? • Readability sucks. • Scala has levels of features. 
43. What’s wrong with Scala? • Backward compatibility – “Scala isn’t binary compatible between minor versions.”
44. What’s wrong with Scala? • Backward compatibility – “Scala isn’t binary compatible between minor versions.”
45. What’s wrong with Scala? • Compilation time > mvn clean install
 … [INFO] Module................................................. SUCCESS [ 7.115 s]
 [INFO] Module................................................. SUCCESS [ 32.680 s]
 [INFO] Module................................................. SUCCESS [01:05 min]
 [INFO] Module................................................. SUCCESS [ 1.080 s]
 [INFO] Module................................................. SUCCESS [ 44.077 s]
 [INFO] Module................................................. SUCCESS [ 1.234 s]
 [INFO] Module................................................. SUCCESS [ 3.410 s]
 [INFO] Module................................................. SUCCESS [ 26.661 s]
 [INFO] Module................................................. SUCCESS [ 45.317 s]
 [INFO] Module................................................. SUCCESS [ 46.435 s]
 [INFO] Module................................................. SUCCESS [ 37.738 s]
 [INFO] Module................................................. SUCCESS [ 14.198 s]
 [INFO] ------------------------------------------------------------------------
 [INFO] BUILD SUCCESS
 [INFO] ------------------------------------------------------------------------
 [INFO] Total time: 06:37 min (Wall Clock)
 [INFO] Finished at: 2017-07-02T15:13:48+03:00
 [INFO] Final Memory: 970M/2498M
 [INFO] ------------------------------------------------------------------------ >
46. What’s wrong with Scala? • Compilation time > mvn clean install | grep min 
 [INFO] Scala............................................... SUCCESS [01:05 min]
 [INFO] Scala............................................... SUCCESS [01:30 min]
 [INFO] Scala............................................... SUCCESS [02:29 min]
 [INFO] Scala............................................... SUCCESS [01:16 min]
 [INFO] Scala............................................... SUCCESS [01:17 min]
 [INFO] Scala............................................... SUCCESS [01:16 min]
 [INFO] Scala............................................... SUCCESS [01:25 min]
 [INFO] Scala............................................... SUCCESS [01:22 min]
 [INFO] Scala............................................... SUCCESS [02:21 min]
 [INFO] Scala............................................... SUCCESS [01:05 min]
 [INFO] Scala............................................... SUCCESS [01:23 min]
 [INFO] Scala............................................... SUCCESS [01:15 min]
 [INFO] Scala............................................... SUCCESS [01:28 min]
 [INFO] Scala............................................... SUCCESS [01:13 min]
 [INFO] Scala............................................... SUCCESS [01:11 min]
 [INFO] Scala............................................... SUCCESS [01:05 min]
 [INFO] Total time: 06:37 min (Wall Clock) >
47. • Readability • Backward compatibility • Compilation time What’s wrong with Scala?
48. There must be also something good about Scala?
49. • (Popular) functional programming on the JVM • Many advanced features There must be also something good about Scala?
50. • We saw some statistics • We learned about boilerplate • We saw some Scala pain points Recap
51. Some more cool features
52. Extension method fun Int.hours() = TimeUnit.HOURS.toMillis(this.toLong()) … 5.hours()
53. Collections val fruits = listOf("banana", "avocado", "apple", "kiwi") fruits .filter { it.startsWith("a") } .sortedBy { it } .map { it.toUpperCase() } .forEach { println(it) }
54. Testing Java @Test public void testShouldProcessCampaign_WhenFlyToInRange() throws Exception { … } Kotlin @Test fun `when "fly to" is in range - should process the campaign`() { TODO() }
55. Why Kotlin? • Concise • Safe • Interoperable • Tool-friendly • Practical
56. • Low entry barriers • Verbose • Popular • Old (but progressing) • Modern • Pragmatic • Inter- operable • FP in the JVM • Advanced features
57. Which one to pick?
59. Questions?
60. Thank You! @OhadShai