[Kotlin] Class etc

Data class - java

public final class UserInfo {

private String name;

private int age;

public UserInfo(String name, int age) {

this.name = name;

this.age = age;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

public String toString() {

return "UserInfo(name = " +this.name + ", age" + this.age + ")";

}

public int hashCode() {

return (this.name != null?this.name.hashCode():0) * 31 + this.age;

}

public boolean equals(Object var1) {

if(obj == this) return true;

if(!(obj instanceof UserInfo)) {

return false;

}

UserInfo userInfo  = (UserInfo) obj;

return userInfo.name.equals(name) &&

userInfo.age == age;

}

}

Data class - kotlin

data class UserInfo(var name : String?, var age : Int?)

싱글톤 구현하기 - Eager initialization

public class Eager {

private static Eager instance = new Eager();

private Eager() {}

public static Eager getInstance() {

return instance;

}

}

public class Lazy {

private static Lazy instance = null;

private Lazy() {}

public static Lazy getInstance() {

if (instance == null) {

instance = new Lazy();

}

return instance;

}

}

// thread safe initialization

public class ThreadSafe {

private static ThreadSafe instance = null;

private ThreadSafe() {

}

public static ThreadSafe getInstance() {

if (instance == null) {

synchronized (ThreadSafe.class) {

if (instance == null) {

instance = new ThreadSafe();

}

}

}

return instance;

}

}

싱글톤 구현하기 - kotlin object

object Eager

- 생성자를 가질 수 없다.

싱글톤 구현하기 - kotlin

class Singleton private constructor(val name : String) {

companion object {

@Volatile private var INSTANCE : Singleton? = null

fun getInstance(name : String) : Singleton = 

INSTANCE ?: synchronized(this) {

INSTANCE ?: Singleton(name).also { INSTANCE = it }

}

}

}

// Lazy 패턴 사용해서 싱글톤 구현

class Lazy {

companion object {

private val INSTANCE : Lazy by lazy {

Lazy()

}

@JvmStatic fun getInstance() = INSTANCE

}

}

// 하지만 값을 넘겨주거나 하지는 못함!!

class 안에 class 정의하기 - Nested class - java에서는 static

class Outer {

private val bar : Int = 1

class Nested {                                     // inner 안써주면 static 써준거와 같음.

fun foo() = 2

}

}

val demo = Outer.Nested().foo()                   // == 2  / Outer 클래스 객체 선언 안해줌

// inner 추가

class Outer {

private val bar : Int = 1

inner class Inner{

fun foo() = bar                             // inner 클래스 정의해줘서 bar 접근 가능

}

}

val demo = Outer().Inner().foo()                   // == 1  / Outer 클래스 객체 선언 해줘야됨!!

Anonymous inner classes 익명 클래스

recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {

override fun onScrolled(recyclerView : RecyclerView?, dx : Int, dy : Int) {

super.onScrolled(recyclerView, dx, dy)

}

override fun onScrollStateChanged(recyclerView : RecyclerView?, newState : Int) {

super.onScrollStateChanged(recyclerView, newState)

}

}