BAEL-1758 Idiomatic Kotlin usage in enum (#4434)

core-kotlin/src/main/kotlin/com/baeldung/enums/CardType.kt

@@ -2,46 +2,21 @@ package com.baeldung.enums
 
 enum class CardType(val color: String) : ICardLimit {
     SILVER("gray") {
-        override fun getCreditLimit(): Int {
-            return 100000
-        }
-
-        override fun calculateCashbackPercent(): Float {
-            return 0.25f
-        }
+        override fun getCreditLimit() = 100000
+        override fun calculateCashbackPercent() = 0.25f
     },
     GOLD("yellow") {
-        override fun getCreditLimit(): Int {
-            return 200000
-        }
-
-        override fun calculateCashbackPercent(): Float {
-            return 0.5f
-        }
+        override fun getCreditLimit() = 200000
+        override fun calculateCashbackPercent(): Float = 0.5f
     },
     PLATINUM("black") {
-        override fun getCreditLimit(): Int {
-            return 300000
-        }
-
-        override fun calculateCashbackPercent(): Float {
-            return 0.75f
-        }
+        override fun getCreditLimit() = 300000
+        override fun calculateCashbackPercent() = 0.75f
     };
 
     companion object {
-        fun getCardTypeByColor(color: String): CardType? {
-            for (cardType in CardType.values()) {
-                if (cardType.color.equals(color)) {
-                    return cardType;
-                }
-            }
-            return null
-        }
-
-        fun getCardTypeByName(name: String): CardType {
-            return CardType.valueOf(name.toUpperCase())
-        }
+        fun getCardTypeByColor(color: String) = values().firstOrNull { it.color == color }
+        fun getCardTypeByName(name: String) = valueOf(name.toUpperCase())
     }
 
     abstract fun calculateCashbackPercent(): Float