And that's that, moving on to android

src/aquarium/generics/Aquarium.kt

@@ -0,0 +1,40 @@
+package aquarium.generics
+
+open class WaterSupply(var needsProcessed: Boolean)
+
+class TapWater : WaterSupply(needsProcessed = true) {
+    fun addChemicalCleaners() {
+        needsProcessed = false
+    }
+}
+
+class FishStoreWater: WaterSupply(needsProcessed = false)
+
+class LakeWater: WaterSupply(needsProcessed = true) {
+    fun filter() {
+        needsProcessed = false
+    }
+}
+
+interface Cleaner<in T: WaterSupply> {
+    fun clean(waterSupply: T)
+}
+
+class TapWaterCleaner: Cleaner<TapWater> {
+    override fun clean(waterSupply: TapWater) {
+        waterSupply.addChemicalCleaners()
+    }
+}
+
+class Aquarium<T: WaterSupply>(val waterSupply: T) {
+    fun addWater(cleaner: Cleaner<T>) {
+        if(waterSupply.needsProcessed) {
+            cleaner.clean(waterSupply)
+        }
+        println("adding water from $waterSupply")
+    }
+
+    inline fun <reified R: WaterSupply> hasWaterSupplyOfType() = waterSupply is R
+}
+
+

src/aquarium/generics/main.kt

@@ -0,0 +1,20 @@
+package aquarium.generics
+
+fun main(args: Array<String>) {
+    genericExample()
+}
+
+fun genericExample() {
+    val cleaner = TapWaterCleaner()
+
+    val aquarium = Aquarium(TapWater())
+    isWaterClean(aquarium)
+    aquarium.addWater(cleaner)
+}
+
+inline fun <reified R: WaterSupply>Aquarium<*>.hasWaterSupplyOfType() = waterSupply is R
+inline fun <reified T: WaterSupply>WaterSupply.isOfType() = this is T
+
+fun <T: WaterSupply>isWaterClean(aquarium: Aquarium<T>) {
+    println("aquarium water is clean: ${aquarium.waterSupply.needsProcessed}")
+}