Java와 함께 사용하는 Kotlin

1. Java৬ ೣԋ ࢎਊೞח Kotlin Taehwan
2. Javaীࢲ Kotlin ࢎਊೡ ٸ • null ઱੄/3೦ध • JvmOverloads • Static Fields • Class ࢚ࣘ
3. null ઱੄
4. null ઱੄ // class name String.kt fun merge(a: String, b: String) = "$a $b"
5. null ઱੄ - javaীࢲ ࠗܳ ٸ // class name String.kt fun merge(a: String, b: String) = "$a $b" public class Sample { @Test public void sample() { System.out.println("merge " + StringKt.merge("A", "B")); } }
6. null ઱੄ - javaীࢲ ࠗܳ ٸ - value // class name String.kt fun merge(a: String, b: String) = "$a $b" public class Sample { private String a = "A"; private String b = "B"; @Test public void sample() { System.out.println("merge " + StringKt.merge(a, b)); } }
7. null ઱੄ - javaীࢲ ࠗܳ ٸ - null value // class name String.kt fun merge(a: String, b: String) = "$a $b" public class Sample { private String a = "A"; private String b = "B"; @Before public void setUp() { a = null; } @Test public void sample() { System.out.println("merge " + StringKt.merge(a, b)); } }
8. null ઱੄ - java ௏٘ value null // class name String.kt fun merge(a: String, b: String) = "$a $b" public class Sample { private String a = "A"; private String b = "B"; @Before public void setUp() { a = null; } @Test public void sample() { System.out.println("merge " + StringKt.merge(a, b)); // java.lang.IllegalArgumentException: // Parameter specified as non-null is null: // method tech.thdev.myapplication.StringKt.merge } }
9. null ઱੄ - javaীࢲ ࠗܳ ٸ - null value // class name String.kt fun merge(a: String, b: String) = "$a $b" public class Sample { private String a = "A"; private String b = "B"; @Before public void setUp() { // a = null; } @Test public void sample() { a = null; System.out.println("merge " + StringKt.merge(a, b)); // ਕ׬ ݫद૑ : Argument 'a' might be null less... } }
10. Ӓېࢲ • nullable ୊ܻ • ? ೞաݶ ୊ܻ оמ // class name String.kt fun merge(a: String?, b: String?) = "$a $b"
11. प೯ೞݶ ׮਺୊ۢ • return : merge null B // class name String.kt fun merge(a: String?, b: String?) = "$a $b"
12. null ୊ܻח? - if != null // class name String.kt fun merge(a: String?, b: String?) = { if (a != null && b != null) { "$a $b" } }
13. null ୊ܻח? - if != null Ѿҗ • return : merge Function0<kotlin.Unit> // class name String.kt fun merge(a: String?, b: String?) = { if (a != null && b != null) { "$a $b" } }
14. null ୊ܻח? - if != null Ѿҗ • return : // class name String.kt fun merge(a: String?, b: String?) = { if (a != null && b != null) { "$a $b" } else { "" } }
15. 3೦ध
16. 3೦ध • java String merge(String a, String b) { return (a != null ? a : "a") + " " + (b != null ? b : "b"); }
17. 3೦ध • java String merge(String a, String b) { return (a != null ? a : "a") + " " + (b != null ? b : "b"); } • kotlin fun merge(a: String?, b: String?) = "${a != null ? a : "a"} ${b != null ? b : "b"}"
18. 3೦ध • java String merge(String a, String b) { return (a != null ? a : "a") + " " + (b != null ? b : "b"); } • kotlin fun merge(a: String?, b: String?) = "${a != null ? a : "a"} ${b != null ? b : "b"}" ޙߨ য়ܨ ߊࢤ
19. 3೦ध - if else ୊ܻೞӝ // class name String.kt fun merge(a: String?, b: String?) = "${if (a != null) a else "a"} ${if (b != null) b else "b"}"
20. 3೦ध - if else ୊ܻೞӝ // class name String.kt fun merge(a: String?, b: String?) = "${if (a != null) a else "a"} ${if (b != null) b else "b"}" ӡযࢲ फযਃ. ઴ৈ઱ࣁਃ.
21. 3೦ध - if else ୊ܻೞӝ // class name String.kt fun merge(a: String?, b: String?) = "${if (a != null) a else "a"} ${if (b != null) b else "b"}" // class name String.kt fun merge(a: String?, b: String?) = "${a ?: "a"} ${b ?: "b"}"
22. null ୊ܻח? - ইې৬ э੉ ୊ܻ೤द׮ • return : merge a B // class name String.kt fun merge(a: String?, b: String?) = "${a ?: "a"} ${b ?: "b"}"
23. Kotlinীࢲ Java ௏٘ ࢎਊೡ ٸח?
24. Kotlinীࢲ Java ௏٘ ࢎਊೡ ٸח? • Annotationਸ ੜ ੸ਊೞ੗ • @Nullable/@NotNull
25. JvmOverloads
26. JvmOverloads class Sample( val name: String, val age: Int = 0, val birthday: String = "2000-01-01") { init { println("name $name age $age birthday $birthday") } }
27. JvmOverloads - javaীࢲ ࠗܰݶ
28. JvmOverloads - javaীࢲ ೣԋ ࢎਊೞ۰ݶ? class Sample( val name: String, val age: Int = 0, val birthday: String = "2000-01-01") { constructor(name: String, age: Int): this(name, age, "2000-01-01") constructor(name: String): this(name, 0) init { println("name $name age $age birthday $birthday") } }
29. JvmOverloads - javaীࢲ ೣԋ ࢎਊೞ۰ݶ?
30. ӡয ӡয ӡয
31. JvmOverloads - @JvmOverloads ୶оೞӝ • @JvmOverloads class Sample @JvmOverloads constructor( val name: String, val age: Int = 0, val birthday: String = "2000-01-01") { init { println("name $name age $age birthday $birthday") } }
32. JvmOverloads - ѾҴ
33. JvmOverloads - function @JvmOverloads fun f(a: String, b: Int = 0, c: String = "abc") { ... }
34. JvmOverloads - function ഐ୹ java void f(String a, int b, String c) { } void f(String a, int b) { } void f(String a) { }
35. Static Fields
36. Static Fields - final static ੿੄ೞӝ • const/@JvmField class Key { companion object { const val TYPE_ZERO = 0 @JvmField val TYPE_ONE = 1 } }
37. Static Fields class Key { companion object { const val TYPE_ZERO = 0 @JvmField val TYPE_ONE = 1 } } // Java class SampleTest { @Test public void sample() { System.out.println(Key.TYPE_ZERO); System.out.println(Key.TYPE_ONE); } }
38. Class ࢚ࣘ
39. Class ࢚ࣘ - Java public class TestOne { public void print() { System.out.println("TestOne"); } }
40. Class ࢚ࣘ - Java > Kotlin public class TestOne { public void print() { System.out.println("TestOne"); } } class TestTwo : TestOne() { override fun print() { super.print() print("TestTwo") } }
41. Class ࢚ࣘ - Java > Kotlin > Java public class TestOne { public void print() { System.out.println("TestOne"); } } class TestTwo : TestOne() { override fun print() { super.print() print("TestTwo") } } public class TestThree extends TestTwo { }
42. Class ࢚ࣘ
43. Class ࢚ࣘ - Error?? • Kotlin ௿ېझח ӝࠄ੸ਵ۽ abstract/interfaceо ইפݶ ࢚ࣘ੉ ࠛо • open੉ۄח ఃਕ٘ܳ ݺद੸ਵ۽ ੸যષਵ۽ॄ ࢚ࣘ੉ оמ
44. Class ࢚ࣘ open class TestTwo : TestOne() { override fun print() { super.print() print("TestTwo") } } public class TestThree extends TestTwo { override fun print() { super.print() print("TestThree") } }
45. End... RGP Koreaীࢲ উ٘۽੉٘ ѐߊ੗ܳ ଺Ҋ ੓ যਃ! kotlin ೣԋ ೞप ࠙!