[BAEL-19882] - Move articles out of core-kotlin part1
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catalin-burcea
9
core-kotlin-modules/core-kotlin-strings/README.md
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9
core-kotlin-modules/core-kotlin-strings/README.md
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## Core Kotlin Strings
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This module contains articles about core Kotlin strings.
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### Relevant articles:
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- [Generate a Random Alphanumeric String in Kotlin](https://www.baeldung.com/kotlin-random-alphanumeric-string)
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- [String Comparison in Kotlin](https://www.baeldung.com/kotlin-string-comparison)
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- [Concatenate Strings in Kotlin](https://www.baeldung.com/kotlin-concatenate-strings)
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- [Kotlin String Templates](https://www.baeldung.com/kotlin-string-template)
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24
core-kotlin-modules/core-kotlin-strings/pom.xml
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core-kotlin-modules/core-kotlin-strings/pom.xml
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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<artifactId>core-kotlin-strings</artifactId>
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<name>core-kotlin-strings</name>
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<packaging>jar</packaging>
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<parent>
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<groupId>com.baeldung.core-kotlin-modules</groupId>
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<artifactId>core-kotlin-modules</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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</parent>
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<dependencies>
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<dependency>
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<groupId>org.apache.commons</groupId>
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<artifactId>commons-lang3</artifactId>
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<version>${commons-lang3.version}</version>
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</dependency>
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</dependencies>
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</project>
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package com.baeldung.stringtemplates
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/**
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* Example of a useful function defined in Kotlin String class
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*/
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fun padExample(): String {
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return "Hello".padEnd(10, '!')
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}
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/**
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* Example of a simple string template usage
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*/
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fun simpleTemplate(n: Int): String {
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val message = "n = $n"
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return message
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}
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/**
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* Example of a string template with a simple expression
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*/
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fun templateWithExpression(n: Int): String {
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val message = "n + 1 = ${n + 1}"
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return message
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}
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/**
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* Example of a string template with expression containing some logic
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*/
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fun templateWithLogic(n: Int): String {
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val message = "$n is ${if (n > 0) "positive" else "not positive"}"
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return message
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}
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/**
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* Example of nested string templates
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*/
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fun nestedTemplates(n: Int): String {
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val message = "$n is ${if (n > 0) "positive" else if (n < 0) "negative and ${if (n % 2 == 0) "even" else "odd"}" else "zero"}"
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return message
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}
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/**
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* Example of joining array's element into a string with a default separator
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*/
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fun templateJoinArray(): String {
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val numbers = listOf(1, 1, 2, 3, 5, 8)
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val message = "first Fibonacci numbers: ${numbers.joinToString()}"
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return message
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}
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/**
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* Example of escaping the dollar sign
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*/
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fun notAStringTemplate(): String {
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val message = "n = \$n"
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return message
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}
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/**
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* Example of a simple triple quoted string
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*/
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fun showFilePath(): String {
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val path = """C:\Repository\read.me"""
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return path
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}
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/**
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* Example of a multiline string
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*/
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fun showMultiline(): String {
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val receipt = """Item 1: $1.00
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Item 2: $0.50"""
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return receipt
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}
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/**
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* Example of a multiline string with indentation
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*/
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fun showMultilineIndent(): String {
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val receipt = """Item 1: $1.00
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>Item 2: $0.50""".trimMargin(">")
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return receipt
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}
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/**
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* Example of a triple quoted string with a not-working escape sequence
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*/
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fun showTripleQuotedWrongEscape(): String {
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val receipt = """Item 1: $1.00\nItem 2: $0.50"""
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return receipt
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}
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/**
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* Example of a triple quoted string with a correctly working escape sequence
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*/
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fun showTripleQuotedCorrectEscape(): String {
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val receipt = """Item 1: $1.00${"\n"}Item 2: $0.50"""
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return receipt
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}
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fun main(args: Array<String>) {
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println(padExample())
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println(simpleTemplate(10))
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println(templateWithExpression(5))
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println(templateWithLogic(7))
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println(nestedTemplates(-5))
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println(templateJoinArray())
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println(notAStringTemplate())
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println(showFilePath())
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println(showMultiline())
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println(showMultilineIndent())
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println(showTripleQuotedWrongEscape())
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println(showTripleQuotedCorrectEscape())
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}
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@@ -0,0 +1,64 @@
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package com.baeldung.randomstring
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import org.apache.commons.lang3.RandomStringUtils
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import org.junit.Before
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import org.junit.jupiter.api.BeforeAll
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import org.junit.jupiter.api.BeforeEach
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import org.junit.jupiter.api.Test
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import java.security.SecureRandom
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import java.util.concurrent.ThreadLocalRandom
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import kotlin.experimental.and
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import kotlin.streams.asSequence
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import kotlin.test.assertEquals
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const val STRING_LENGTH = 10
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const val ALPHANUMERIC_REGEX = "[a-zA-Z0-9]+"
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class RandomStringUnitTest {
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private val charPool : List<Char> = ('a'..'z') + ('A'..'Z') + ('0'..'9')
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@Test
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fun givenAStringLength_whenUsingJava_thenReturnAlphanumericString() {
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var randomString = ThreadLocalRandom.current()
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.ints(STRING_LENGTH.toLong(), 0, charPool.size)
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.asSequence()
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.map(charPool::get)
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.joinToString("")
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assert(randomString.matches(Regex(ALPHANUMERIC_REGEX)))
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assertEquals(STRING_LENGTH, randomString.length)
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}
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@Test
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fun givenAStringLength_whenUsingKotlin_thenReturnAlphanumericString() {
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var randomString = (1..STRING_LENGTH).map { i -> kotlin.random.Random.nextInt(0, charPool.size) }
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.map(charPool::get)
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.joinToString("")
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assert(randomString.matches(Regex(ALPHANUMERIC_REGEX)))
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assertEquals(STRING_LENGTH, randomString.length)
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}
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@Test
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fun givenAStringLength_whenUsingApacheCommon_thenReturnAlphanumericString() {
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var randomString = RandomStringUtils.randomAlphanumeric(STRING_LENGTH)
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assert(randomString.matches(Regex(ALPHANUMERIC_REGEX)))
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assertEquals(STRING_LENGTH, randomString.length)
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}
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@Test
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fun givenAStringLength_whenUsingRandomForBytes_thenReturnAlphanumericString() {
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val random = SecureRandom()
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val bytes = ByteArray(STRING_LENGTH)
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random.nextBytes(bytes)
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var randomString = (0..bytes.size - 1).map { i ->
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charPool.get((bytes[i] and 0xFF.toByte() and (charPool.size-1).toByte()).toInt())
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}.joinToString("")
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assert(randomString.matches(Regex(ALPHANUMERIC_REGEX)))
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assertEquals(STRING_LENGTH, randomString.length)
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}
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}
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@@ -0,0 +1,47 @@
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package com.baeldung.stringcomparison
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import org.junit.Test
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import kotlin.test.assertFalse
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import kotlin.test.assertTrue
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class StringComparisonUnitTest {
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@Test
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fun `compare using equals operator`() {
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val first = "kotlin"
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val second = "kotlin"
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val firstCapitalized = "KOTLIN"
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assertTrue { first == second }
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assertFalse { first == firstCapitalized }
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}
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@Test
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fun `compare using referential equals operator`() {
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val first = "kotlin"
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val second = "kotlin"
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val copyOfFirst = buildString { "kotlin" }
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assertTrue { first === second }
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assertFalse { first === copyOfFirst }
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}
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@Test
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fun `compare using equals method`() {
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val first = "kotlin"
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val second = "kotlin"
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val firstCapitalized = "KOTLIN"
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assertTrue { first.equals(second) }
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assertFalse { first.equals(firstCapitalized) }
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assertTrue { first.equals(firstCapitalized, true) }
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}
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@Test
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fun `compare using compare method`() {
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val first = "kotlin"
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val second = "kotlin"
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val firstCapitalized = "KOTLIN"
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assertTrue { first.compareTo(second) == 0 }
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assertTrue { first.compareTo(firstCapitalized) == 32 }
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assertTrue { firstCapitalized.compareTo(first) == -32 }
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assertTrue { first.compareTo(firstCapitalized, true) == 0 }
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}
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}
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@@ -0,0 +1,48 @@
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package com.baeldung.stringconcatenation
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import org.junit.Test
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import kotlin.test.assertEquals
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class StringConcatenationTest {
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@Test
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fun givenTwoStrings_concatenateWithTemplates_thenEquals() {
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val a = "Hello"
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val b = "Baeldung"
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val c = "$a $b"
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assertEquals("Hello Baeldung", c)
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}
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@Test
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fun givenTwoStrings_concatenateWithPlusOperator_thenEquals() {
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val a = "Hello"
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val b = "Baeldung"
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val c = a + " " + b
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assertEquals("Hello Baeldung", c)
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}
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@Test
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fun givenTwoStrings_concatenateWithStringBuilder_thenEquals() {
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val a = "Hello"
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val b = "Baeldung"
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val builder = StringBuilder()
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builder.append(a).append(" ").append(b)
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val c = builder.toString()
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assertEquals("Hello Baeldung", c)
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}
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@Test
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fun givenTwoStrings_concatenateWithPlusMethod_thenEquals() {
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val a = "Hello"
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val b = "Baeldung"
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val c = a.plus(" ").plus(b)
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assertEquals("Hello Baeldung", c)
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}
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}
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