Java와 함께 사용하는 Kotlin

Transcript

1. Java৬ ೣԋ ࢎਊೞח Kotlin
   Taehwan
   

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2. Javaীࢲ Kotlin ࢎਊೡ ٸ
   • null ઱੄/3೦ध
   • JvmOverloads
   • Static Fields
   • Class ࢚ࣘ
   

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3. null ઱੄
   

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4. null ઱੄
   // class name String.kt
   fun merge(a: String, b: String) = "$a $b"
   

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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"));
   }
   }
   

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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));
   }
   }
   

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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));
   }
   }
   

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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
   }
   }
   

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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...
   }
   }
   

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10. Ӓېࢲ
    • nullable ୊ܻ
    • ? ೞաݶ ୊ܻ оמ
    // class name String.kt
    fun merge(a: String?, b: String?) = "$a $b"
    

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11. प೯ೞݶ ׮਺୊ۢ
    • return : merge null B
    // class name String.kt
    fun merge(a: String?, b: String?) = "$a $b"
    

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12. null ୊ܻח? - if != null
    // class name String.kt
    fun merge(a: String?, b: String?) = {
    if (a != null && b != null) {
    "$a $b"
    }
    }
    

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13. null ୊ܻח? - if != null Ѿҗ
    • return : merge Function0
    // class name String.kt
    fun merge(a: String?, b: String?) = {
    if (a != null && b != null) {
    "$a $b"
    }
    }
    

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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 {
    ""
    }
    }
    

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15. 3೦ध
    

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16. 3೦ध
    • java
    String merge(String a, String b) {
    return (a != null ? a : "a") + " " + (b != null ? b : "b");
    }
    

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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"}"
    

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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
    

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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"}"
    

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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.
    

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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"}"
    

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22. null ୊ܻח? - ইې৬ э੉ ୊ܻ೤द׮
    • return : merge a B
    // class name String.kt
    fun merge(a: String?, b: String?)
    = "${a ?: "a"} ${b ?: "b"}"
    

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23. Kotlinীࢲ Java ௏٘ ࢎਊೡ ٸח?
    

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24. Kotlinীࢲ Java ௏٘ ࢎਊೡ ٸח?
    • Annotationਸ ੜ ੸ਊೞ੗
    • @Nullable/@NotNull
    

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25. JvmOverloads
    

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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")
    }
    }
    

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27. JvmOverloads - javaীࢲ ࠗܰݶ
    

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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")
    }
    }
    

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29. JvmOverloads - javaীࢲ ೣԋ ࢎਊೞ۰ݶ?
    

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30. ӡয ӡয ӡয
    

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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")
    }
    }
    

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32. JvmOverloads - ѾҴ
    

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33. JvmOverloads - function
    @JvmOverloads fun f(a: String, b: Int = 0, c: String = "abc") {
    ...
    }
    

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34. JvmOverloads - function ഐ୹ java
    void f(String a, int b, String c) { }
    void f(String a, int b) { }
    void f(String a) { }
    

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35. Static Fields
    

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36. Static Fields - final static ੿੄ೞӝ
    • const/@JvmField
    class Key {
    companion object {
    const val TYPE_ZERO = 0
    @JvmField val TYPE_ONE = 1
    }
    }
    

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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);
    }
    }
    

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38. Class ࢚ࣘ
    

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39. Class ࢚ࣘ - Java
    public class TestOne {
    public void print() {
    System.out.println("TestOne");
    }
    }
    

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40. Class ࢚ࣘ - Java > Kotlin
    public class TestOne {
    public void print() {
    System.out.println("TestOne");
    }
    }
    class TestTwo : TestOne() {
    override fun print() {
    super.print()
    print("TestTwo")
    }
    }
    

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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 {
    }
    

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42. Class ࢚ࣘ
    

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43. Class ࢚ࣘ - Error??
    • Kotlin ௿ېझח ӝࠄ੸ਵ۽ abstract/interfaceо ইפݶ ࢚ࣘ੉ ࠛо
    • open੉ۄח ఃਕ٘ܳ ݺद੸ਵ۽ ੸যષਵ۽ॄ ࢚ࣘ੉ оמ
    

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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")
    }
    }
    

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45. End...
    RGP Koreaীࢲ উ٘۽੉٘ ѐߊ੗ܳ ଺Ҋ ੓
    যਃ!
    kotlin ೣԋ ೞप ࠙!
    

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