A Dive into Kotlin.

A basic intro into the Kotlin Programming language and it's subtle yet powerful features over Java.

Transcript

1. A dive into Ashish Krishnan @ashishkrishnan / Github / Twitter Android @ Kite
3. Kotlin by JetBrains
4. Kotlin 1. Statically - typed 2. Runs on JVM 3. Production ready 4. Expressive 5. Pragmatic 6. Open Source
5. Kotlin 1. Statically - typed 2. Runs on JVM 3. Production ready 4. Expressive 5. Pragmatic 6. Open Source
6. Kotlin 1. Statically - typed 2. Runs on JVM 3. Production ready 4. Expressive 5. Pragmatic 6. Open Source
7. Kotlin 1. Statically - typed 2. Runs on JVM 3. Production ready 4. Expressive 5. Pragmatic 6. Open Source
8. Kotlin 1. Statically - typed 2. Runs on JVM 3. Production ready 4. Expressive 5. Pragmatic 6. Open Source
9. Kotlin 1. Statically - typed 2. Runs on JVM 3. Production ready 4. Expressive 5. Pragmatic 6. Open Source (~600k) https://github.com/JetBrains/kotlin
10. Why Kotlin?
11. POJOs
12. public class Person { String name; int age; String email; public Person(String name, int age, String email) { this.name = name; this.age = age; this.email = email; } public String getName() { return name; } public void setName(String name) { this.name = name; }
13. public class Person { String name; int age; String email; public Person(String name, int age, String email) { this.name = name; this.age = age; this.email = email; } public String getName() { return name; } public void setName(String name) { this.name = name; }
14. public class Person { String name; int age; String email; public Person(String name, int age, String email) { this.name = name; this.age = age; this.email = email; } public String getName() { // } public void setName(String name) { // }
15. @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Person person = (Person) o; // more code } @Override public int hashCode() { int result = name != null ? name.hashCode() : 0; // return result; } @Override public String toString() { return ; // more code } }
16. @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Person person = (Person) o; // more code } @Override public int hashCode() { int result = name != null ? name.hashCode() : 0; // return result; } @Override public String toString() { return ; // more code } }
17. @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Person person = (Person) o; // more code } @Override public int hashCode() { int result = name != null ? name.hashCode() : 0; // return result; } @Override public String toString() { return ; // more code } }
18. POKOs
19. data class Person( val name: String, val age: Int, val company: String ) Short & Sweet
20. data class Person( val name: String, val age: Int, val company: String ) Short & Sweet
21. data class Person( val name: String, val age: Int, val company: String ) Short & Sweet
22. data class Person( val name: String, val age: Int, val company: String ) Short & Sweet - getters - setters - equals() - hashCode() - toString() - constructors
24. val listOfPersons = /* ……… */ val peopleNamedAshish = listOfPersons.filter { it == “Foo” } Short & Sweet
25. val listOfPersons = /* ……… */ val peopleNamedAshish = listOfPersons.filter { it == “Foo” } Short & Sweet
26. val listOfPersons = /* ……… */ val peopleNamedAshish = listOfPersons.filter { it == “Foo” } Short & Sweet
27. Kotlin is Interoperable with Java
28. Talking to Java fun main(args: Array<String>) { val customer = CustomerJava() customer.email = "ashish@kite.work" val runnable = Runnable { println("Invoking runnable") } val kr = KotlinCustomerRepo() val customerJava = kr.getById(10) }
29. Talking to Java fun main(args: Array<String>) { val customer = CustomerJava() customer.email = "ashish@kite.work" val runnable = Runnable { println("Invoking runnable") } val kr = KotlinCustomerRepo() val customerJava = kr.getById(10) }
30. Talking to Java fun main(args: Array<String>) { val customer = CustomerJava() customer.email = "ashish@kite.work" val runnable = Runnable { println("Invoking runnable") } val kr = KotlinCustomerRepo() val customerJava = kr.getById(10) }
31. public static void main(String[] args) { CustomerKotlin customerKotlin = new CustomerKotlin(1, "Ashish", "ashish@xyz.com"); customerKotlin.setEmail(“ashish@kite.work"); } Talking to Kotlin
32. public static void main(String[] args) { CustomerKotlin customerKotlin = new CustomerKotlin(1, "Ashish", "ashish@xyz.com"); customerKotlin.setEmail(“ashish@kite.work"); } Talking to Kotlin
34. Kotlin is Safe
35. var name: String = "kotlin" name = null // compiler is not happy var name: String? = "kotlin" name = null // happy Dealing with Nulls
36. var name: String = "kotlin" name = null // compiler is not happy var name: String? = "kotlin" name = null // happy Dealing with Nulls
37. var name: String = "kotlin" name = null // compiler is not happy var name: String? = "kotlin" name = null // happy name?.length -> Safe call Dealing with Nulls
38. val length = name?.length ?: -1 -> Elvis Operator val length = name!!.length -> For NPE Lovers, not-null assertion Dealing with Nulls
39. Kotlin good-to-haves
40. String Interpolation String name = "Ashish"; String company = "Kite"; System.out.println("Hi, I am " + name + "and I fly Android at " + company);
41. String Interpolation val name = "Ashish"; val company = "Kite"; println("Hi, I am $name and I fly Android at $company");
42. when when (number) { 1 -> print("number is 1") 2 -> print("number is 2") 3, 4 -> print("number is 3 or 4") in 5 .. 10 -> print("number is 5, 6, 7, 8, 9, or 10") else -> print("number is out of range") }
43. when when (number) { 1 -> print("number is 1") 2 -> print("number is 2") 3, 4 -> print("number is 3 or 4") in 5 .. 10 -> print("number is 5, 6, 7, 8, 9, or 10") else -> print("number is out of range") }
44. when when (number) { 1 -> print("number is 1") 2 -> print("number is 2") 3, 4 -> print("number is 3 or 4") in 5 .. 10 -> print("number is 5, 6, 7, 8, 9, or 10") else -> print("number is out of range") }
45. when when (number) { 1 -> print("number is 1") 2 -> print("number is 2") 3, 4 -> print("number is 3 or 4") in 5 .. 10 -> print("number is 5, 6, 7, 8, 9, or 10") else -> print("number is out of range") }
46. Extension Functions fun String.toTitleCase(): String { return this.toLowerCase().capitalize() } fun String?.toTitleCase(): String? { return this.toLowerCase().capitalize() }
47. Extension Functions fun String.toTitleCase(): String { return this.toLowerCase().capitalize() } fun String?.toTitleCase(): String? { return this.toLowerCase().capitalize() }
48. Extension Functions fun String.toTitleCase(): String { return this.toLowerCase().capitalize() } fun String?.toTitleCase(): String? { return this.toLowerCase().capitalize() }
49. Default Arguments values public void hello(String name) { if (name == null) { name = "World"; } System.out.print("Hello, " + name + "!"); }
50. Default Arguments values public void hello(String name) { if (name == null) { name = "World"; } System.out.print("Hello, " + name + "!"); } fun hello(name: String = "World") { println("Hello, $name!") }
51. Named parameters fun main(args: Array<String>) { openFile("file.txt", readOnly = true) } fun openFile(filename: String, readOnly: Boolean) : File { // custom }
52. Named parameters fun main(args: Array<String>) { openFile("file.txt", readOnly = true) } fun openFile(filename: String, readOnly: Boolean) : File { // custom }
53. Named parameters fun main(args: Array<String>) { openFile("file.txt", readOnly = true) } fun openFile(filename: String, readOnly: Boolean) : File { // custom }
54. Optional Parameters fun printDetails(name: String, email: String = "", phone: String = "NA") { println( /* code */) } fun main(args: Array<String>) { printDetails("Ashish", phone = "999 123", email = "ashish@kite.work") }
55. Optional Parameters fun printDetails(name: String, email: String = "", phone: String = "NA") { println( /* code */) } fun main(args: Array<String>) { printDetails("Ashish", phone = "999 123", email = "ashish@kite.work") printDetails("Ashish", phone = "999 123") }
56. Lambdas val sum = { x: Int, y: Int -> x + y } // type: (Int, Int) -> Int val result = sum(10, 20) numbers.filter({ number -> number.isPrime() }) numbers.filter { number -> number.isPrime() } numbers.filter { it.isPrime() } persons .filter { it.age >= 18 } .sortedBy { it.name } .map { it.email } .forEach { print(it) }
57. Lambdas val sum = { x: Int, y: Int -> x + y } // type: (Int, Int) -> Int val result = sum(10, 20) numbers.filter({ number -> number.isPrime() }) numbers.filter { number -> number.isPrime() } numbers.filter { it.isPrime() } persons .filter { it.age >= 18 } .sortedBy { it.name } .map { it.email } .forEach { print(it) }
58. Lambdas val sum = { x: Int, y: Int -> x + y } // type: (Int, Int) -> Int val result = sum(10, 20) numbers.filter({ number -> number.isPrime() }) numbers.filter { number -> number.isPrime() } numbers.filter { it.isPrime() } persons .filter { it.age >= 20 } .sortedBy { it.name } .map { it.email } .forEach { print(it) }
59. Using Kotlin
60. Using Kotlin • For Android • For the Server • For the Web • Kotlin Native
61. Using Kotlin • For Android • For the Server • For the Web • Kotlin Native
62. Using Kotlin • For Android • For the Server • For the Web • Kotlin Native
63. Using Kotlin • For Android • For the Server • For the Web • Kotlin Native
64. Following Kotlin • Official Blog - https://blog.jetbrains.com/kotlin/ • Official Slack - https://slack.kotlinlang.org/
65. Thank you @ashishkrishnan / Twitter / Github mailto: ashish@kite.work