Kotlin Nested and Inner Classes Code SampleCode

Issue: BAEL-1759

core-kotlin/src/main/kotlin/com/baeldung/nested/Computer.kt

@@ -0,0 +1,75 @@
+package com.baeldung.nested
+
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+
+class Computer(val model: String) {
+
+    companion object {
+        const val originCountry = "China"
+        fun getBuiltDate(): String {
+            return "2018-05-23"
+        }
+
+        val log: Logger = LoggerFactory.getLogger(Computer::class.java)
+    }
+
+    //Nested class
+    class MotherBoard(val manufacturer: String) {
+        fun getInfo() = "Made by $manufacturer installed in $originCountry - ${getBuiltDate()}"
+    }
+
+    //Inner class
+    inner class HardDisk(val sizeInGb: Int) {
+        fun getInfo() = "Installed on ${this@Computer} with $sizeInGb GB"
+    }
+
+    interface Switcher {
+        fun on(): String
+    }
+
+    interface Protector {
+        fun smart()
+    }
+
+    fun powerOn(): String {
+        //Local class
+        var defaultColor = "Blue"
+
+        class Led(val color: String) {
+            fun blink(): String {
+                return "blinking $color"
+            }
+
+            fun changeDefaultPowerOnColor() {
+                defaultColor = "Violet"
+            }
+        }
+
+        val powerLed = Led("Green")
+        log.debug("defaultColor is $defaultColor")
+        powerLed.changeDefaultPowerOnColor()
+        log.debug("defaultColor changed inside Led class to $defaultColor")
+        //Anonymous object
+        val powerSwitch = object : Switcher, Protector {
+            override fun on(): String {
+                return powerLed.blink()
+            }
+
+            override fun smart() {
+                log.debug("Smart protection is implemented")
+            }
+
+            fun changeDefaultPowerOnColor() {
+                defaultColor = "Yellow"
+            }
+        }
+        powerSwitch.changeDefaultPowerOnColor()
+        log.debug("defaultColor changed inside powerSwitch anonymous object to $defaultColor")
+        return powerSwitch.on()
+    }
+
+    override fun toString(): String {
+        return "Computer(model=$model)"
+    }
+}

core-kotlin/src/test/kotlin/com/baeldung/nested/ComputerUnitTest.kt

@@ -0,0 +1,28 @@
+package com.baeldung.nested
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+
+class ComputerUnitTest {
+
+    @Test
+    fun givenComputer_whenPowerOn_thenBlink() {
+        val computer = Computer("Desktop")
+
+        assertThat(computer.powerOn()).isEqualTo("blinking Green")
+    }
+
+    @Test
+    fun givenMotherboard_whenGetInfo_thenGetInstalledAndBuiltDetails() {
+        val motherBoard = Computer.MotherBoard("MotherBoard Inc.")
+
+        assertThat(motherBoard.getInfo()).isEqualTo("Made by MotherBoard Inc. installed in China - 2018-05-23")
+    }
+
+    @Test
+    fun givenHardDisk_whenGetInfo_thenGetComputerModelAndDiskSizeInGb() {
+        val hardDisk = Computer("Desktop").HardDisk(1000)
+
+        assertThat(hardDisk.getInfo()).isEqualTo("Installed on Computer(model=Desktop) with 1000 GB")
+    }
+}