Merge pull request #9436 from anirban99/feature/ktln-43/working-with-lists-in-kotlin
KTLN-43 : Working with lists in Kotlin
This commit is contained in:
Josh Cummings
GitHub
commit
118786c62a
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package com.baeldung.kotlin.collections
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import kotlin.collections.List
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class ListExample {
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private val countries = listOf("Germany", "India", "Japan", "Brazil", "Australia")
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private val cities = mutableListOf("Berlin", "Calcutta", "Seoul", "Sao Paulo", "Sydney")
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fun createList(): List<String> {
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val countryList = listOf("Germany", "India", "Japan", "Brazil")
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return countryList
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}
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fun createMutableList(): MutableList<String> {
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val cityList = mutableListOf("Berlin", "Calcutta", "Seoul", "Sao Paulo")
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return cityList
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}
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fun iterateUsingForEachLoop(): List<Int> {
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val countryLength = mutableListOf<Int>()
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countries.forEach { it ->
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print("$it ")
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println(" Length: ${it.length}")
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countryLength.add(it.length)
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}
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return countryLength
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}
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fun iterateUsingForLoop(): List<Int> {
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val countryLength = mutableListOf<Int>()
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for (country in countries) {
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print("$country ")
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println(" Length: ${country.length}")
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countryLength.add(country.length)
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}
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return countryLength
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}
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fun iterateUsingForLoopRange(): List<Int> {
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val countryLength = mutableListOf<Int>()
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for (i in 0 until countries.size) {
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print("${countries[i]} ")
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println(" Length: ${countries[i].length}")
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countryLength.add(countries[i].length)
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}
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return countryLength
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}
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fun iterateUsingForEachIndexedLoop(): List<Int> {
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val countryLength = mutableListOf<Int>()
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countries.forEachIndexed { i, e ->
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println("country[$i] = $e")
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print(" Index: $i")
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println(" Length: ${e.length}")
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countryLength.add(e.length)
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}
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return countryLength
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}
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fun iterateUsingListIterator() {
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val iterator = countries.listIterator()
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while (iterator.hasNext()) {
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val country = iterator.next()
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print("$country ")
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}
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println()
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while (iterator.hasPrevious()) {
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println("Index: ${iterator.previousIndex()}")
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}
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}
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fun iterateUsingIterator() {
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val iterator = cities.iterator()
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iterator.next()
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iterator.remove()
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println(cities)
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}
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fun iterateUsingMutableListIterator() {
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val iterator = cities.listIterator(1)
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iterator.next()
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iterator.add("London")
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iterator.next()
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iterator.set("Milan")
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println(cities)
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}
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fun retrieveElementsInList(): String {
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println(countries[2])
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return countries[2]
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}
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fun retrieveElementsUsingGet(): String {
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println(countries.get(3))
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return countries.get(3)
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}
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fun retrieveElementsFirstAndLast(): String? {
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println(countries.first())
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println(countries.last())
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println(countries.first { it.length > 7 })
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println(countries.last { it.startsWith("J") })
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println(countries.firstOrNull { it.length > 8 })
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return countries.firstOrNull { it.length > 8 }
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}
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fun retrieveSubList(): List<String> {
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val subList = countries.subList(1, 4)
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println(subList)
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return subList
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}
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fun retrieveListSliceUsingIndices(): List<String> {
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val sliceList = countries.slice(1..4)
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println(sliceList)
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return sliceList
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}
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fun retrieveListSliceUsingIndicesList(): List<String> {
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val sliceList = countries.slice(listOf(1, 4))
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println(sliceList)
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return sliceList
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}
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fun countList(): Int {
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val count = countries.count()
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println(count)
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return count
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}
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fun countListUsingPredicate(): Int {
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val count = countries.count { it.length > 5 }
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println(count)
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return count
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}
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fun countListUsingProperty(): Int {
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val size = countries.size
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println(size)
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return size
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}
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fun addToList(): List<String> {
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cities.add("Barcelona")
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println(cities)
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cities.add(3, "London")
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println(cities)
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cities.addAll(listOf("Singapore", "Moscow"))
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println(cities)
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cities.addAll(2, listOf("Prague", "Amsterdam"))
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println(cities)
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return cities
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}
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fun removeFromList(): List<String> {
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cities.remove("Seoul")
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println(cities)
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cities.removeAt(1)
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println(cities)
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return cities
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}
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fun replaceFromList(): List<String> {
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cities.set(3, "Prague")
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println(cities)
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cities[4] = "Moscow"
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println(cities)
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cities.fill("Barcelona")
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println(cities)
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return cities
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}
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fun sortMutableList(): List<String> {
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cities.sort()
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println(cities)
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cities.sortDescending()
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println(cities)
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return cities
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}
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fun sortList(): List<String> {
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val sortedCountries = countries.sorted()
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println("countries = $countries")
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println("sortedCountries = $sortedCountries")
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val sortedCountriesDescending = countries.sortedDescending()
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println("countries = $countries")
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println("sortedCountriesDescending = $sortedCountriesDescending")
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return sortedCountriesDescending
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}
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fun checkOneElementInList(): Boolean {
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return countries.contains("Germany")
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}
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fun checkOneElementInListUsingOperator(): Boolean {
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return "Spain" in countries
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}
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fun checkElementsInList(): Boolean {
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return cities.containsAll(listOf("Calcutta", "Sao Paulo", "Sydney"))
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}
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}
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@ -0,0 +1,126 @@
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package com.baeldung.kotlin.collections
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import org.junit.jupiter.api.Test
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import org.junit.jupiter.api.Assertions.assertEquals
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import kotlin.test.assertFalse
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import kotlin.test.assertTrue
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class ListExampleUnitTest {
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private val classUnderTest: ListExample = ListExample()
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@Test
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fun whenListIsCreated_thenContainsElements() {
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assertTrue(classUnderTest.createList().contains("India"))
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assertTrue(classUnderTest.createMutableList().contains("Seoul"))
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}
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@Test
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fun whenIterateUsingForEachLoop_thenSuccess() {
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assertEquals(7, classUnderTest.iterateUsingForEachLoop()[0])
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}
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@Test
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fun whenIterateUsingForLoop_thenSuccess() {
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assertEquals(5, classUnderTest.iterateUsingForLoop()[1])
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}
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@Test
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fun whenIterateUsingForLoopRange_thenSuccess() {
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assertEquals(6, classUnderTest.iterateUsingForLoopRange()[3])
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}
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@Test
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fun whenIterateUsingForEachIndexedLoop_thenSuccess() {
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assertEquals(9, classUnderTest.iterateUsingForEachIndexedLoop()[4])
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}
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@Test
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fun whenRetrieveElementsInList_thenSuccess() {
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assertEquals("Japan", classUnderTest.retrieveElementsInList())
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}
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@Test
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fun whenRetrieveElementsUsingGet_thenSuccess() {
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assertEquals("Brazil", classUnderTest.retrieveElementsUsingGet())
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}
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@Test
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fun whenRetrieveElementsFirstAndLast_thenSuccess() {
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assertEquals("Australia", classUnderTest.retrieveElementsFirstAndLast())
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}
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@Test
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fun whenRetrieveSubList_thenSuccess() {
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assertEquals(3, classUnderTest.retrieveSubList().size)
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}
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@Test
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fun whenRetrieveListSliceUsingIndices_thenSuccess() {
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assertEquals(4, classUnderTest.retrieveListSliceUsingIndices().size)
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}
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@Test
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fun whenRetrieveListSliceUsingIndicesList_thenSuccess() {
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assertEquals(2, classUnderTest.retrieveListSliceUsingIndicesList().size)
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}
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@Test
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fun whenCountList_thenSuccess() {
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assertEquals(5, classUnderTest.countList())
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}
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@Test
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fun whenCountListUsingPredicate_thenSuccess() {
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assertEquals(3, classUnderTest.countListUsingPredicate())
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}
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@Test
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fun whenCountListUsingProperty_thenSuccess() {
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assertEquals(5, classUnderTest.countListUsingProperty())
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}
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@Test
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fun whenAddToList_thenSuccess() {
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assertEquals(11, classUnderTest.addToList().count())
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}
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@Test
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fun whenRemoveFromList_thenSuccess() {
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val list = classUnderTest.removeFromList()
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assertEquals(3, list.size)
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assertEquals("Sao Paulo", list[1])
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}
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@Test
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fun whenReplaceFromList_thenSuccess() {
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val list = classUnderTest.replaceFromList()
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assertEquals(5, list.size)
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assertEquals("Barcelona", list[1])
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}
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@Test
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fun whenSortMutableList_thenSuccess() {
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assertEquals("Sydney", classUnderTest.sortMutableList()[0])
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}
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@Test
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fun whenSortList_thenSuccess() {
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assertEquals("India", classUnderTest.sortList()[1])
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}
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@Test
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fun whenCheckOneElementInList_thenSuccess() {
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assertTrue(classUnderTest.checkOneElementInList())
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}
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@Test
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fun whenCheckOneElementInListUsingOperator_thenSuccess() {
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assertFalse(classUnderTest.checkOneElementInListUsingOperator())
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}
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@Test
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fun whenCheckElementsInList_thenSuccess() {
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assertTrue(classUnderTest.checkElementsInList())
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}
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}
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@ -11,5 +11,6 @@ This module contains articles about core features in the Kotlin language.
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- [Lazy Initialization in Kotlin](https://www.baeldung.com/kotlin-lazy-initialization)
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- [Comprehensive Guide to Null Safety in Kotlin](https://www.baeldung.com/kotlin-null-safety)
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- [Kotlin Scope Functions](https://www.baeldung.com/kotlin-scope-functions)
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- [If-Else Expression in Kotlin](https://www.baeldung.com/kotlin/if-else-expression)
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- [Checking Whether a lateinit var Is Initialized in Kotlin](https://www.baeldung.com/kotlin/checking-lateinit)
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- [[<-- Prev]](/core-kotlin-modules/core-kotlin-lang)
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- [[<-- Prev]](/core-kotlin-modules/core-kotlin-lang)
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