add when and smartcast

Author: jjeanjacques10

README.md

@@ -135,6 +135,33 @@ class Game(val name: String,
 
 Example: [05-classes.kt](./examples/05-classes.kt)
 
+## Lists
+
+There is some ways to create lists in Kotlin
+
+````kotlin
+var digimons = mutableListOf("Agumon", "Tailmon", "Angemon")
+var digimons = listOf("Agumon", "Tailmon", "Angemon")
+val digimonPower: MutableMap<Int, Int> = mutableMapOf(0 to 50, 1 to 50, 2 to 100)
+````
+
+## When
+
+When is similar Java Switch
+
+``` kotlin
+fun getPrice(console: Console): Int =
+ when (console) {
+ Console.GBA -> 1000
+ Console.PLAYSTATION -> 5299
+ Console.SWITCH -> 2500
+ Console.XBOX -> 4200
+ Console.PC -> 5000
+ }
+```
+
+Example: [06-when.k](./examples/06-when.kt)
+
 ## References
 
 - [Learn the Kotlin programming language](https://developer.android.com/kotlin/learn?gclsrc=aw.ds&gclid=CjwKCAjw9e6SBhB2EiwA5myr9tk-mZhoAytl5-3nJeQ0lgYnyIGcs5GFh9-aN1tDvkwvcrFEAJZdLhoC0lAQAvD_BwE)

examples/04-enums.kts

@@ -1,15 +1,17 @@
-enum class Console {
- GBA,
- PLAYSTATION,
- XBOX,
- SWITCH,
- PC
+enum class Console(val year: Int) {
+ GBA(2003),
+ PLAYSTATION(2000),
+ XBOX(2005),
+ SWITCH(2017),
+ PC(1946)
 }
 
-class Game(val name: String,
- val console: Console) {
+class Game(
+ val name: String,
+ val console: Console
+) {
  fun play(): String {
- return "You're playing $name on $console"
+ return "You're playing $name on $console (realeased at ${console.year})"
  }
 }
 

examples/06-when.kt

@@ -0,0 +1,31 @@
+enum class Console(val year: Int) {
+ GBA(2003),
+ PLAYSTATION(2000),
+ XBOX(2005),
+ SWITCH(2017),
+ PC(1946)
+}
+
+fun getPrice(console: Console): Int =
+ when (console) {
+ Console.GBA -> 1000
+ Console.PLAYSTATION -> 5299
+ Console.SWITCH -> 2500
+ Console.XBOX -> 4200
+ Console.PC -> 5000
+ }
+
+fun haveDiscount(console: Console): String {
+ return when (console) {
+ Console.GBA, Console.SWITCH, Console.PC -> "have discount"
+ Console.PLAYSTATION, Console.XBOX -> "not have discount"
+ }
+}
+
+fun main() {
+ val price = getPrice(Console.PLAYSTATION)
+ println("Console price is R$$price and this console ${haveDiscount(Console.PLAYSTATION)}")
+
+ val pricePC = getPrice(Console.PC)
+ println("Console price is R$$pricePC and this console ${haveDiscount(Console.PC)}")
+}

examples/07-smartcast.kt

@@ -0,0 +1,34 @@
+interface Expression
+class Number(val value: Int) : Expression
+class Sum(val left: Expression, val right: Expression) : Expression
+
+/*
+fun exam(expression: Expression): Int {
+ if (expression is Number) {
+ // There is a smart cast here
+ return expression.value
+ }
+
+ if (expression is Sum) {
+ // There is a smart cast here
+ return exam(expression.left) + exam(expression.right)
+ }
+
+ throw IllegalArgumentException("Expression is invalid")
+}*/
+
+fun exam(expression: Expression): Int =
+ when (expression) {
+ is Number -> {
+ print("Expression with number: ${expression.value}")
+ expression.value // Last expression in block will be returned as a result
+ }
+ is Sum -> exam(expression.left) + exam(expression.right)
+ else -> throw IllegalArgumentException("Expression is invalid")
+ }
+
+fun main() {
+ // ((1+2) + 4)
+ val result = exam(Sum(Sum(Number(1), Number(2)), Number(4)))
+ println("Result: $result")
+}

projects/spring-boot/src/main/kotlin/com/jjeanjacques/digimon/controller/DigimonController.kt

@@ -0,0 +1,28 @@
+package com.jjeanjacques.digimon.controller
+
+import com.jjeanjacques.digimon.controller.dto.DigimonPowerDTO
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.RequestMapping
+import org.springframework.web.bind.annotation.RestController
+import org.springframework.http.ResponseEntity
+
+@RestController
+@RequestMapping("/digimon")
+class DigimonController {
+
+ @GetMapping
+ fun listAll(): ResponseEntity<Any> {
+ val response = ArrayList<DigimonPowerDTO>()
+
+ var digimons = listOf("Agumon", "Tailmon", "Angemon")
+ val digimonPower: MutableMap<Int, Int> = mutableMapOf(0 to 50, 1 to 50, 2 to 100)
+
+ var i: Int = 0
+ digimons.forEach {
+ val digimonPowerDTO = DigimonPowerDTO(it, digimonPower[i]!!)
+ response.add(digimonPowerDTO)
+ i++
+ }
+ return ResponseEntity.ok(response)
+ }
+}

projects/spring-boot/src/main/kotlin/com/jjeanjacques/digimon/controller/dto/DigimonPowerDTO.kt

@@ -0,0 +1,3 @@
+package com.jjeanjacques.digimon.controller.dto
+
+data class DigimonPowerDTO(val name: String, val power: Int)