Klean Code with Kotlin

1. Klean Code with Kotlin
2. IS THERE A DOCTOR IN THE AUDIENCE?
3. IS THERE A DOCTOR JAVA DEVELOPER IN THE AUDIENCE?
4. Should I start using Kotlin?
5. TL;DL* - YES! *Too Long; Didn’t Listen
6. • Look at trends • Compare Kotlin to Java • More Kotlin features Plan B
7. Google Trends - Kotlin
13. Why do developers ❤ Kotlin?
15. 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.
16. Boilerplate boilerplate - little or no alteration. verbose a lot of code to do minimal jobs.
17. Java is Verbose
18. IDE
19. Hello Kotlin! Java public class Hello { public static void main(String[] args) { System.out.println("Hello!"); } } Kotlin fun main() { println("Hello!") }
20. POJO Class Java public class AdCpcData { private int adId; private double cpc; }
21. 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; } }
22. 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()…
23. 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()…
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; } @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
25. 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 )
26. Variable declaration Java private final Map<String, String> myMap = new HashMap<>(); myMap.put("Hi", "There"); Kotlin val myMap = mapOf("Hi" to "There")
27. Testing Java @Test public void testShouldProcessCampaign_WhenFlyToInRange() throws Exception { … } Kotlin @Test fun `when "fly to" is in range - should process the campaign`() { TODO() }
28. Java vs Kotlin • Many more boilerplate examples… • But Java do make some progress…
30. • We saw some statistics • We learned about boilerplate Recap
31. Some more cool features
32. Extension method fun Int.hours() = TimeUnit.HOURS.toMillis(this.toLong()) … 5.hours()
33. Collections val fruits = listOf("banana", "avocado", "apple", "kiwi") fruits .filter { it.startsWith("a") } .sortedBy { it } .map { it.toUpperCase() } .forEach { println(it) }
34. When Expression when (object) { 1 -> "One" "Hello" -> "Greeting" is Long -> "Long" in 2..10 -> "obj is in the range" else -> "Unknown" }
35. Inter-Op with Java Java adCpcData.getAdId() Kotlin adCpcData.adId
36. Null Safety val world: String? = null println(world.toUpperCase()) // In Java you will get NPE // In Kotlin you will get compilation error
37. Null Safety val world: String? = null if (world != null) { println(world.toUpperCase()) } // In Java you will get NPE // In Kotlin you will get compilation error
38. Many More Features • String Interpolation • Named Parameters • Smart Casting • Contracts • Multiline Strings
39. Why Kotlin? • Concise • Safe • Interoperable • Tool-friendly • Practical
41. ⌘ + ⌥ + ⇧ + K
42. Questions?
43. Thank You! @OhadShai