Паттерны Singleton, Decorator, Command, Builder

src/main/kotlin/ru/otus/homework/builder.kt

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+package ru.otus.homework
+
+/**
+ * Паттерн Builder
+ */
+
+class House(
+    private var floors: Int,
+    private var area: Double,
+    private var painting: Boolean?,
+    private var material: String?
+) {
+    private constructor(builder: Builder) : this(builder.floors, builder.area, builder.painting, builder.material)
+
+    companion object {
+        inline fun build(floors: Int, area: Double, otherParam: Builder.() -> Unit) = Builder(floors, area).apply(otherParam).build()
+    }
+    class Builder(var floors: Int, var area: Double) {
+        var painting: Boolean? = null
+        var material: String? = null
+
+        fun build(): House {
+            return House(this)
+        }
+    }
+
+    override fun toString(): String {
+        return """Ваш новый дом 
+            Этажей: ${this.floors}
+            Площадь: ${this.area}
+            Покраска: ${this.painting}
+            Материал стен: ${this.material}
+            """
+    }
+}
+
+fun main() {
+
+    val house1 = House.build(2, 200.0){}
+    println(house1)
+
+    // вариант создания дома с доп параметрами
+    val house2 = House.build(1, 150.0) { material="кирпич"; painting=true }
+    println(house2)
+}

src/main/kotlin/ru/otus/homework/command.kt

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+package ru.otus.homework
+
+/**
+ * Паттерн Command
+ */
+
+interface Command {
+    fun execute()
+}
+
+class OpenCommand(val device: Device) : Command {
+    override fun execute() {
+        device.unlockDevice()
+    }
+}
+class LockAllCommand(val device: ArrayList<Device>) : Command {
+    override fun execute() {
+        device.forEach { it.lockDevice() }
+    }
+}
+
+
+interface Device {
+    fun unlockDevice()
+    fun lockDevice()
+}
+
+class Safe : Device {
+    override fun unlockDevice() {
+        println("Сейф открыт")
+    }
+
+    override fun lockDevice() {
+        println("Сейф закрыт")
+    }
+}
+
+
+class SmartDoor : Device {
+    override fun unlockDevice() {
+        println("Дверь разблокирована")
+    }
+
+    override fun lockDevice() {
+        println("Дверь заблокирована")
+    }
+}
+
+class Switcher(var c:Command) {
+    fun accept() {
+        c.execute()
+    }
+}
+
+fun main() {
+    val safeDevice : Device = Safe()     // сейф
+    val cmdOpenSafe = OpenCommand(safeDevice)
+    val switcherSafe = Switcher(cmdOpenSafe)
+    switcherSafe.accept() // откроем сейф
+
+    val smartDoor : Device = SmartDoor() // умная дверь
+    val cmdOpenDoor = OpenCommand(smartDoor)
+    val switcherDoor = Switcher(cmdOpenDoor)
+    switcherDoor.accept() // откроем дверь
+
+    // все сразу закроем
+    val allDevices = ArrayList<Device>()
+    allDevices.add(safeDevice)
+    allDevices.add(smartDoor)
+    val cmdAllLock = LockAllCommand(allDevices)
+    val switchAll = Switcher(cmdAllLock)
+    switchAll.accept()
+}

src/main/kotlin/ru/otus/homework/decorator.kt

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+package ru.otus.homework
+
+/**
+ * Паттерн Decorator на примере шиномнтажа))
+ */
+interface TireService {
+    fun description(): String
+    fun cost(): Double
+}
+
+class ChangeTire : TireService {
+    override fun description(): String {
+        return "Замена колеса (снять/поставить)"
+    }
+
+    override fun cost(): Double {
+        return 1000.0
+    }
+}
+
+class RepairTire : TireService {
+    override fun description(): String {
+        return "Ремонт прокола шины"
+    }
+
+    override fun cost(): Double {
+        return 300.0
+    }
+}
+
+abstract class DecoratorAddService(private val service: TireService) : TireService {
+    abstract override fun description(): String
+
+    abstract override fun cost(): Double
+}
+
+class Difficult(private val service: TireService) : DecoratorAddService(service) {
+    override fun description(): String {
+        return service.description() + ", высокая сложность работы"
+    }
+
+    override fun cost(): Double {
+        return service.cost() + 500.0
+    }
+}
+
+class VipClient(private val service: TireService) : DecoratorAddService(service) {
+    override fun description(): String {
+        return service.description() + ", VIP"
+    }
+
+    override fun cost(): Double {
+        return service.cost() + 1000.0
+    }
+}
+
+fun main() {
+    println("Шинка СУПЕР")
+    val changeTire : TireService  = ChangeTire() // замена колес
+    println("${changeTire.description()} = ${changeTire.cost()}")
+
+    var repairTire : TireService = RepairTire() // ремонт колес
+    repairTire = Difficult(repairTire)    // + сложность
+    repairTire = VipClient(repairTire)    // + vip обслуживание
+
+    println("${repairTire.description()} = ${repairTire.cost()}")
+}

src/main/kotlin/ru/otus/homework/singleton.kt

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+package ru.otus.homework
+
+/**
+ * Паттерн Singleton
+ */
+class Singleton private constructor() {
+
+    companion object {
+        private var instance : Singleton? = null
+        fun getInstance(): Singleton {
+            if (instance == null) {
+                instance = Singleton()
+            }
+            return instance!!
+        }
+    }
+
+}
+
+fun main() {
+    // получим единственный экземпляр объекта
+    val single = Singleton.getInstance()
+}