Added functions for iterating and retrieving elements

core-kotlin-modules/core-kotlin-collections/src/main/kotlin/com/baeldung/collections/ListExample.kt

@@ -3,11 +3,86 @@ package com.baeldung.collections
 import kotlin.collections.List
 
 class ListExample {
+
+    private val countries = listOf("Germany", "India", "Japan", "Brazil", "Australia")
+    private val cities = mutableListOf("Berlin", "Calcutta", "Seoul", "Sao Paulo", "Sydney")
+
     fun createList(): List<String> {
-        return listOf("one", "two", "three")
+        val countryList = listOf("Germany", "India", "Japan", "Brazil")
+        return countryList
     }
 
     fun createMutableList(): MutableList<String> {
-        return mutableListOf("Berlin", "Kolkata", "London")
+        val cityList = mutableListOf("Berlin", "Calcutta", "Seoul", "Sao Paulo")
+        return cityList
+    }
+
+    fun iterateUsingForLoop() {
+        countries.forEach { it -> print("$it ") }
+        println()
+
+        for (country in countries) {
+            print("$country ")
+        }
+        println()
+
+        for (i in 0 until countries.size) {
+            print("${countries[i]} ")
+        }
+        println()
+
+        countries.forEachIndexed { i, e ->
+            println("country[$i] = $e")
         }
     }
+
+    fun iterateUsingListIterator() {
+        val iterator = countries.listIterator()
+        while (iterator.hasNext()) {
+            val country = iterator.next()
+            print("$country ")
+        }
+        println()
+
+        while (iterator.hasPrevious()) {
+            println("Index: ${iterator.previousIndex()}")
+        }
+    }
+
+    fun iterateUsingIterator() {
+        val iterator = cities.iterator()
+        iterator.next()
+        iterator.remove()
+        println(cities)
+    }
+
+    fun iterateUsingMutableListIterator() {
+        val iterator = cities.listIterator(1)
+        iterator.next()
+        iterator.add("London")
+        iterator.next()
+        iterator.set("Milan")
+        println(cities)
+    }
+
+    fun retrieveElementsInList(): String {
+        println(countries[2])
+        return countries[2]
+    }
+
+    fun retrieveElementsUsingGet(): String {
+        println(countries.get(3))
+        return countries.get(3)
+    }
+
+    fun retrieveElementsFirstAndLast(): String? {
+        println(countries.first())
+        println(countries.last())
+        println(countries.first { it.length > 7 })
+        println(countries.last { it.startsWith("J") })
+        println(countries.firstOrNull { it.length > 8 })
+        return countries.firstOrNull { it.length > 8 }
+    }
+
+    //5. Retrieve parts of the list
+}

core-kotlin-modules/core-kotlin-collections/src/test/kotlin/com/baeldung/collections/ListExampleUnitTest.kt

@@ -3,6 +3,7 @@ package com.baeldung.collections
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertNotEquals
+import kotlin.test.assertNull
 import kotlin.test.assertTrue
 
 class ListExampleUnitTest {
@@ -11,8 +12,22 @@ class ListExampleUnitTest {
 
     @Test
     fun whenListIsCreated_thenContainsElements() {
-        assertTrue(classUnderTest.createList().contains("two"))
-        assertTrue(classUnderTest.createMutableList().contains("Berlin"))
+        assertTrue(classUnderTest.createList().contains("India"))
+        assertTrue(classUnderTest.createMutableList().contains("Seoul"))
     }
 
+    @Test
+    fun whenRetrieveElementsInList_thenSuccess() {
+        assertEquals("Japan", classUnderTest.retrieveElementsInList())
+    }
+
+    @Test
+    fun whenRetrieveElementsUsingGet_thenSuccess() {
+        assertEquals("Brazil", classUnderTest.retrieveElementsUsingGet())
+    }
+
+    @Test
+    fun whenRetrieveElementsFirstAndLast_thenSuccess() {
+        assertEquals("Australia", classUnderTest.retrieveElementsFirstAndLast())
+    }
 }