patterns

src/main/kotlin/Builder.kt

@@ -0,0 +1,48 @@
+class Product(private val name: String, private val price: Double, private val weight: Double, private val color: String) {
+    override fun toString(): String {
+        return "Product(name='$name', price=$price, weight=$weight, color='$color')"
+    }
+}
+
+class ProductBuilder {
+    private var name: String = ""
+    private var price: Double = 0.0
+    private var weight: Double = 0.0
+    private var color: String = ""
+
+    fun setName(name: String): ProductBuilder {
+        this.name = name
+        return this
+    }
+
+    fun setPrice(price: Double): ProductBuilder {
+        this.price = price
+        return this
+    }
+
+    fun setWeight(weight: Double): ProductBuilder {
+        this.weight = weight
+        return this
+    }
+
+    fun setColor(color: String): ProductBuilder {
+        this.color = color
+        return this
+    }
+
+    fun build(): Product {
+        return Product(name, price, weight, color)
+    }
+}
+
+fun main() {
+
+    val product = ProductBuilder()
+        .setName("Example Product")
+        .setPrice(50.5)
+        .setWeight(2.2)
+        .setColor("Red")
+        .build()
+
+    println(product)
+}

src/main/kotlin/Command.kt

@@ -0,0 +1,56 @@
+interface Command {
+    fun execute()
+}
+
+class LightOnCommand(private val light: Light) : Command {
+    override fun execute() {
+        light.on()
+    }
+}
+
+class LightOffCommand(private val light: Light) : Command {
+    override fun execute() {
+        light.off()
+    }
+}
+
+
+class Light {
+    fun on() {
+        println("Light on")
+    }
+
+    fun off() {
+        println("Light off")
+    }
+}
+
+
+class RemoteControl {
+    private val commands = mutableListOf<Command>()
+
+    fun setCommand(command: Command) {
+        commands.add(command)
+    }
+
+    fun executeCommands() {
+        for (command in commands) {
+            command.execute()
+        }
+        commands.clear()
+    }
+}
+
+
+fun main() {
+    val remoteControl = RemoteControl()
+
+    val light = Light()
+    val lightOnCommand = LightOnCommand(light)
+    val lightOffCommand = LightOffCommand(light)
+
+    remoteControl.setCommand(lightOnCommand)
+    remoteControl.setCommand(lightOffCommand)
+
+    remoteControl.executeCommands()
+}

src/main/kotlin/Decorator.kt

@@ -0,0 +1,58 @@
+
+interface Coffee {
+    fun cost(): Double
+    fun ingredients(): String
+}
+
+
+class SimpleCoffee : Coffee {
+    override fun cost(): Double {
+        return 1.0
+    }
+
+    override fun ingredients(): String {
+        return "Simple coffee"
+    }
+}
+
+abstract class CoffeeDecorator(private val decoratedCoffee: Coffee) : Coffee {
+    override fun cost(): Double {
+        return decoratedCoffee.cost()
+    }
+
+    override fun ingredients(): String {
+        return decoratedCoffee.ingredients()
+    }
+}
+
+
+class Milk(private val decoratedCoffee: Coffee) : CoffeeDecorator(decoratedCoffee) {
+    override fun cost(): Double {
+        return super.cost() + 0.5
+    }
+
+    override fun ingredients(): String {
+        return super.ingredients() + ", Milk"
+    }
+}
+
+
+class Whip(private val decoratedCoffee: Coffee) : CoffeeDecorator(decoratedCoffee) {
+    override fun cost(): Double {
+        return super.cost() + 0.7
+    }
+
+    override fun ingredients(): String {
+        return super.ingredients() + ", Whip"
+    }
+}
+
+fun main() {
+
+    var someCoffee: Coffee = SimpleCoffee()
+
+    someCoffee = Milk(someCoffee)
+    someCoffee = Whip(someCoffee)
+
+    println("Cost: ${someCoffee.cost()}; Ingredients: ${someCoffee.ingredients()}")
+}

src/main/kotlin/Singleton.kt

@@ -0,0 +1,11 @@
+class Singleton private constructor() {
+    companion object {
+        val instance: Singleton by lazy { Singleton() }
+    }
+}
+fun main() {
+    val singleton: Singleton = Singleton.instance
+    val singleton2: Singleton = Singleton.instance
+
+    println(singleton === singleton2)
+}