Merge branch 'master' of https://github.com/JonCook/tutorials

core-kotlin-2/.gitignore

@@ -0,0 +1,14 @@
+/bin/
+
+#ignore gradle
+.gradle/
+
+
+#ignore build and generated files
+build/
+node/
+out/
+
+#ignore installed node modules and package lock file
+node_modules/
+package-lock.json

core-kotlin-2/README.md

@@ -0,0 +1,15 @@
+## Core Kotlin
+
+This module contains articles about core Kotlin.
+
+### Relevant articles:
+
+- [Void Type in Kotlin](https://www.baeldung.com/kotlin-void-type)
+- [How to use Kotlin Range Expressions](https://www.baeldung.com/kotlin-ranges)
+- [Creating a Kotlin Range Iterator on a Custom Object](https://www.baeldung.com/kotlin-custom-range-iterator)
+- [Kotlin Scope Functions](https://www.baeldung.com/kotlin-scope-functions)
+- [Kotlin Annotations](https://www.baeldung.com/kotlin-annotations)
+- [Split a List into Parts in Kotlin](https://www.baeldung.com/kotlin-split-list-into-parts)
+- [String Comparison in Kotlin](https://www.baeldung.com/kotlin-string-comparison)
+- [Guide to JVM Platform Annotations in Kotlin](https://www.baeldung.com/kotlin-jvm-annotations)
+- More articles: [[<-- prev]](/core-kotlin)

core-kotlin-2/build.gradle

@@ -0,0 +1,58 @@
+
+
+group 'com.baeldung.ktor'
+version '1.0-SNAPSHOT'
+
+
+buildscript {
+    ext.kotlin_version = '1.3.30'
+
+    repositories {
+        mavenCentral()
+    }
+    dependencies {
+
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+apply plugin: 'java'
+apply plugin: 'kotlin'
+apply plugin: 'application'
+
+mainClassName = 'APIServer.kt'
+
+sourceCompatibility = 1.8
+compileKotlin { kotlinOptions.jvmTarget = "1.8" }
+compileTestKotlin { kotlinOptions.jvmTarget = "1.8" }
+
+repositories {
+    mavenCentral()
+    jcenter()
+    maven { url "https://dl.bintray.com/kotlin/ktor" }
+}
+sourceSets {
+    main{
+        kotlin{
+            srcDirs 'com/baeldung/ktor'
+        }
+    }
+}
+
+test {
+    useJUnitPlatform()
+    testLogging {
+        events "passed", "skipped", "failed"
+    }
+}
+
+dependencies {
+    implementation "ch.qos.logback:logback-classic:1.2.1"
+    implementation "org.jetbrains.kotlin:kotlin-stdlib:${kotlin_version}"
+    testImplementation 'org.junit.jupiter:junit-jupiter:5.4.2'
+    testImplementation 'junit:junit:4.12'
+    testImplementation 'org.assertj:assertj-core:3.12.2'
+    testImplementation 'org.mockito:mockito-core:2.27.0'
+    testImplementation "org.jetbrains.kotlin:kotlin-test:${kotlin_version}"
+    testImplementation "org.jetbrains.kotlin:kotlin-test-junit5:${kotlin_version}"
+}

core-kotlin-2/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.4-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

core-kotlin-2/gradlew

@@ -0,0 +1,188 @@
+#!/usr/bin/env sh
+
+#
+# Copyright 2015 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"

core-kotlin-2/gradlew.bat

@@ -0,0 +1,100 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      http://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

core-kotlin-2/pom.xml

@@ -0,0 +1,97 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-kotlin-2</artifactId>
+    <name>core-kotlin-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-kotlin</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../parent-kotlin</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-stdlib-jdk8</artifactId>
+            <version>${kotlin.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit.jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <version>${mockito.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>net.bytebuddy</groupId>
+            <artifactId>byte-buddy</artifactId>
+            <version>${byte-buddy.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-test</artifactId>
+            <version>${kotlin.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-test-junit5</artifactId>
+            <version>${kotlin.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.jetbrains.kotlin</groupId>
+                <artifactId>kotlin-maven-plugin</artifactId>
+                <version>${kotlin.version}</version>
+                <executions>
+                    <execution>
+                        <id>compile</id>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>test-compile</id>
+                        <phase>test-compile</phase>
+                        <goals>
+                            <goal>test-compile</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <jvmTarget>1.8</jvmTarget>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <kotlin.version>1.3.30</kotlin.version>
+        <junit.jupiter.version>5.4.2</junit.jupiter.version>
+        <mockito.version>2.27.0</mockito.version>
+        <byte-buddy.version>1.9.12</byte-buddy.version>
+        <assertj.version>3.10.0</assertj.version>
+    </properties>
+
+</project>

core-kotlin-2/resources/logback.xml

@@ -0,0 +1,11 @@
+<configuration>
+  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+    <encoder>
+      <pattern>%d{YYYY-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+    </encoder>
+  </appender>
+
+  <root level="INFO">
+    <appender-ref ref="STDOUT"/>
+  </root>
+</configuration>

core-kotlin-2/settings.gradle

@@ -0,0 +1,2 @@
+rootProject.name = 'KtorWithKotlin'
+

core-kotlin-2/src/main/kotlin/com/baeldung/annotations/Annotations.kt

@@ -0,0 +1,7 @@
+package com.baeldung.annotations
+
+@Target(AnnotationTarget.FIELD)
+annotation class Positive
+
+@Target(AnnotationTarget.FIELD)
+annotation class AllowedNames(val names: Array<String>)

core-kotlin-2/src/main/kotlin/com/baeldung/annotations/Item.kt

@@ -0,0 +1,3 @@
+package com.baeldung.annotations
+
+class Item(@Positive val amount: Float, @AllowedNames(["Alice", "Bob"]) val name: String)

core-kotlin-2/src/main/kotlin/com/baeldung/annotations/Main.kt

@@ -0,0 +1,7 @@
+package com.baeldung.annotations
+
+fun main(args: Array<String>) {
+    val item = Item(amount = 1.0f, name = "Bob")
+    val validator = Validator()
+    println("Is instance valid? ${validator.isValid(item)}")
+}

core-kotlin-2/src/main/kotlin/com/baeldung/annotations/Validator.kt

@@ -0,0 +1,38 @@
+package com.baeldung.annotations
+
+/**
+ * Naive annotation-based validator.
+ * @author A.Shcherbakov
+ */
+class Validator() {
+
+    /**
+     * Return true if every item's property annotated with @Positive is positive and if
+     * every item's property annotated with @AllowedNames has a value specified in that annotation.
+     */
+    fun isValid(item: Item): Boolean {
+        val fields = item::class.java.declaredFields
+        for (field in fields) {
+            field.isAccessible = true
+            for (annotation in field.annotations) {
+                val value = field.get(item)
+                if (field.isAnnotationPresent(Positive::class.java)) {
+                    val amount = value as Float
+                    if (amount < 0) {
+                        return false
+                    }
+                }
+                if (field.isAnnotationPresent(AllowedNames::class.java)) {
+                    val allowedNames = field.getAnnotation(AllowedNames::class.java)?.names
+                    val name = value as String
+                    allowedNames?.let {
+                        if (!it.contains(name)) {
+                            return false
+                        }
+                    }
+                }
+            }
+        }
+        return true
+    }
+}

core-kotlin-2/src/main/kotlin/com/baeldung/jvmannotations/Document.kt

@@ -0,0 +1,11 @@
+package com.baeldung.jvmannotations
+
+import java.util.*
+
+interface Document {
+
+    @JvmDefault
+    fun getTypeDefault() = "document"
+
+    fun getType() = "document"
+}

core-kotlin-2/src/main/kotlin/com/baeldung/jvmannotations/HtmlDocument.java

@@ -0,0 +1,9 @@
+package com.baeldung.jvmannotations;
+
+public class HtmlDocument implements Document {
+
+    @Override
+    public String getType() {
+        return "HTML";
+    }
+}

core-kotlin-2/src/main/kotlin/com/baeldung/jvmannotations/Message.kt

@@ -0,0 +1,66 @@
+@file:JvmName("MessageHelper")
+@file:JvmMultifileClass //used
+package com.baeldung.jvmannotations
+
+import java.util.*
+
+@JvmName("getMyUsername")
+fun getMyName() : String {
+    return "myUserId"
+}
+
+object MessageBroker {
+    @JvmStatic
+    var totalMessagesSent = 0
+
+    const val maxMessageLength = 0
+
+    @JvmStatic
+    fun clearAllMessages() {
+    }
+
+    @JvmStatic
+    @JvmOverloads
+    @Throws(Exception::class)
+    fun findMessages(sender : String, type : String = "text", maxResults : Int = 10) : List<Message> {
+        if(sender.isEmpty()) {
+            throw Exception()
+        }
+        return ArrayList()
+    }
+}
+
+class Message {
+
+    // this would cause a compilation error since sender is immutable
+    // @set:JvmName("setSender")
+    val sender = "myself"
+
+    // this works as name is overridden
+    @JvmName("getSenderName")
+    fun getSender() : String = "from:$sender"
+
+    @get:JvmName("getReceiverName")
+    @set:JvmName("setReceiverName")
+    var receiver : String = ""
+
+    @get:JvmName("getContent")
+    @set:JvmName("setContent")
+    var text = ""
+
+    // generates a warning
+    @get:JvmName("getId")
+    private val id = 0
+
+    @get:JvmName("hasAttachment")
+    var hasAttachment = true
+
+    var isEncrypted = true
+
+    fun setReceivers(receiverNames : List<String>) {
+    }
+
+    @JvmName("setReceiverIds")
+    fun setReceivers(receiverNames : List<Int>) {
+    }
+}

core-kotlin-2/src/main/kotlin/com/baeldung/jvmannotations/MessageConverter.kt

@@ -0,0 +1,6 @@
+@file:JvmMultifileClass
+@file:JvmName("MessageHelper") //applies to all top level functions / variables / constants
+package com.baeldung.jvmannotations
+
+fun convert(message: Message) {
+}

core-kotlin-2/src/main/kotlin/com/baeldung/jvmannotations/TextDocument.kt

@@ -0,0 +1,16 @@
+package com.baeldung.jvmannotations
+
+import java.util.*
+class TextDocument : Document {
+    override fun getType() = "text"
+
+    fun transformList(list : List<Number>) : List<Number> {
+        return list.filter { n -> n.toInt() > 1 }
+    }
+
+    fun transformListInverseWildcards(list : List<@JvmSuppressWildcards Number>) : List<@JvmWildcard Number> {
+        return list.filter { n -> n.toInt() > 1 }
+    }
+
+    var list : List<@JvmWildcard Any> = ArrayList()
+}

core-kotlin-2/src/main/kotlin/com/baeldung/jvmannotations/XmlDocument.kt

@@ -0,0 +1,5 @@
+package com.baeldung.jvmannotations
+
+import java.util.*
+
+class XmlDocument(d : Document) : Document by d

core-kotlin-2/src/main/kotlin/com/baeldung/range/CharRange.kt

@@ -0,0 +1,13 @@
+package com.baeldung.range
+
+fun main(args: Array<String>) {
+
+    for (ch in 'a'..'f') {
+        print(ch)
+    }
+    println()
+
+    for (ch in 'f' downTo 'a') {
+        print(ch)
+    }
+}

core-kotlin-2/src/main/kotlin/com/baeldung/range/Color.kt

@@ -0,0 +1,21 @@
+package com.baeldung.range
+
+enum class Color(val rgb: Int) {
+    BLUE(0x0000FF),
+    GREEN(0x008000),
+    RED(0xFF0000),
+    MAGENTA(0xFF00FF),
+    YELLOW(0xFFFF00);
+}
+
+fun main(args: Array<String>) {
+
+    println(Color.values().toList());
+    val red = Color.RED
+    val yellow = Color.YELLOW
+    val range = red..yellow
+
+    println(range.contains(Color.MAGENTA))
+    println(range.contains(Color.BLUE))
+    println(range.contains(Color.GREEN))
+}

core-kotlin-2/src/main/kotlin/com/baeldung/range/CustomColor.kt

@@ -0,0 +1,56 @@
+package com.baeldung.range
+
+import java.lang.IllegalStateException
+
+class CustomColor(val rgb: Int): Comparable<CustomColor> {
+
+    override fun compareTo(other: CustomColor): Int {
+        return this.rgb.compareTo(other.rgb)
+    }
+
+    operator fun rangeTo(that: CustomColor) = ColorRange(this,that)
+
+    operator fun inc(): CustomColor {
+        return CustomColor(rgb + 1)
+    }
+
+    init {
+        if(rgb < 0x000000 || rgb > 0xFFFFFF){
+            throw IllegalStateException("RGB must be between 0 and 16777215")
+        }
+    }
+
+    override fun toString(): String {
+        return "CustomColor(rgb=$rgb)"
+    }
+}
+class ColorRange(override val start: CustomColor,
+                override val endInclusive: CustomColor) : ClosedRange<CustomColor>, Iterable<CustomColor>{
+
+    override fun iterator(): Iterator<CustomColor> {
+        return ColorIterator(start, endInclusive)
+    }
+}
+
+class ColorIterator(val start: CustomColor, val endInclusive: CustomColor) : Iterator<CustomColor> {
+
+    var initValue = start
+
+    override fun hasNext(): Boolean {
+        return initValue <= endInclusive
+    }
+
+    override fun next(): CustomColor {
+        return initValue++
+    }
+}
+
+fun main(args: Array<String>) {
+    val a = CustomColor(0xABCDEF)
+    val b = CustomColor(-1)
+    val c = CustomColor(0xABCDFF)
+
+    for(color in a..c){
+        println(color)
+    }
+}

core-kotlin-2/src/main/kotlin/com/baeldung/range/Filter.kt

@@ -0,0 +1,18 @@
+package com.baeldung.range
+
+fun main(args: Array<String>) {
+    val r = 1..10
+
+    //Apply filter
+    val f = r.filter { it -> it % 2 == 0 }
+    println(f)
+
+    //Map
+    val m = r.map { it -> it * it }
+    println(m)
+
+    //Reduce
+    val rdc = r.reduce { a, b -> a + b }
+    println(rdc)
+
+}

core-kotlin-2/src/main/kotlin/com/baeldung/range/FirstLast.kt

@@ -0,0 +1,8 @@
+package com.baeldung.range
+
+fun main(args: Array<String>) {
+
+    println((1..9).first)
+    println((1..9 step 2).step)
+    println((3..9).reversed().last)
+}

core-kotlin-2/src/main/kotlin/com/baeldung/range/OtherRangeFunctions.kt

@@ -0,0 +1,14 @@
+package com.baeldung.range
+
+fun main(args: Array<String>) {
+
+    val r = 1..20
+    println(r.min())
+    println(r.max())
+    println(r.sum())
+    println(r.average())
+    println(r.count())
+
+    val repeated = listOf(1, 1, 2, 4, 4, 6, 10)
+    println(repeated.distinct())
+}

core-kotlin-2/src/main/kotlin/com/baeldung/range/Range.kt

@@ -0,0 +1,28 @@
+package com.baeldung.range
+
+fun main(args: Array<String>) {
+
+    for (i in 1..9) {
+        print(i)
+    }
+    println()
+
+    for (i in 9 downTo 1) {
+        print(i)
+    }
+    println()
+
+    for (i in 1.rangeTo(9)) {
+        print(i)
+    }
+    println()
+
+    for (i in 9.downTo(1)) {
+        print(i)
+    }
+    println()
+
+    for (i in 1 until 9) {
+        print(i)
+    }
+}

core-kotlin-2/src/main/kotlin/com/baeldung/range/ReverseRange.kt

@@ -0,0 +1,14 @@
+package com.baeldung.range
+
+fun main(args: Array<String>) {
+
+    (1..9).reversed().forEach {
+        print(it)
+    }
+
+    println()
+
+    (1..9).reversed().step(3).forEach {
+        print(it)
+    }
+}

core-kotlin-2/src/main/kotlin/com/baeldung/range/Step.kt

@@ -0,0 +1,15 @@
+package com.baeldung.range
+
+fun main(args: Array<String>) {
+
+    for(i in 1..9 step 2){
+        print(i)
+    }
+
+    println()
+
+    for (i in 9 downTo 1 step 2){
+        print(i)
+    }
+
+}

core-kotlin-2/src/main/kotlin/com/baeldung/range/UntilRange.kt

@@ -0,0 +1,8 @@
+package com.baeldung.range
+
+fun main(args: Array<String>) {
+
+    for (i in 1 until 9) {
+        print(i)
+    }
+}

core-kotlin-2/src/main/kotlin/com/baeldung/scope/ScopeFunctions.kt

@@ -0,0 +1,25 @@
+package com.baeldung.scope
+
+data class Student(var studentId: String = "", var name: String = "", var surname: String = "") {
+}
+
+data class Teacher(var teacherId: Int = 0, var name: String = "", var surname: String = "") {
+    fun setId(anId: Int): Teacher = apply { teacherId = anId }
+    fun setName(aName: String): Teacher = apply { name = aName }
+    fun setSurname(aSurname: String): Teacher = apply { surname = aSurname }
+}
+
+data class Headers(val headerInfo: String)
+
+data class Response(val headers: Headers)
+
+data class RestClient(val url: String) {
+    fun getResponse() = Response(Headers("some header info"))
+}
+
+data class BankAccount(val id: Int) {
+    fun checkAuthorization(username: String) = Unit
+    fun addPayee(payee: String) = Unit
+    fun makePayment(paymentDetails: String) = Unit
+
+}

core-kotlin-2/src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

core-kotlin-2/src/test/kotlin/com/baeldung/annotations/ValidationTest.kt

@@ -0,0 +1,41 @@
+package com.baeldung.annotations
+
+import org.junit.Test
+import kotlin.test.assertTrue
+import kotlin.test.assertFalse
+
+class ValidationTest {
+
+    @Test
+    fun whenAmountIsOneAndNameIsAlice_thenTrue() {
+        assertTrue(Validator().isValid(Item(1f, "Alice")))
+    }
+
+    @Test
+    fun whenAmountIsOneAndNameIsBob_thenTrue() {
+        assertTrue(Validator().isValid(Item(1f, "Bob")))
+    }
+
+
+    @Test
+    fun whenAmountIsMinusOneAndNameIsAlice_thenFalse() {
+        assertFalse(Validator().isValid(Item(-1f, "Alice")))
+    }
+
+    @Test
+    fun whenAmountIsMinusOneAndNameIsBob_thenFalse() {
+        assertFalse(Validator().isValid(Item(-1f, "Bob")))
+    }
+
+    @Test
+    fun whenAmountIsOneAndNameIsTom_thenFalse() {
+        assertFalse(Validator().isValid(Item(1f, "Tom")))
+    }
+
+    @Test
+    fun whenAmountIsMinusOneAndNameIsTom_thenFalse() {
+        assertFalse(Validator().isValid(Item(-1f, "Tom")))
+    }
+
+
+}

core-kotlin-2/src/test/kotlin/com/baeldung/lists/ListsUnitTest.kt

@@ -0,0 +1,34 @@
+package com.baeldung.lists
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class ListsUnitTest {
+
+    var batmans: List<String> = listOf("Christian Bale", "Michael Keaton", "Ben Affleck", "George Clooney")
+
+    @Test
+    fun whenFindASpecificItem_thenItemIsReturned() {
+        //Returns the first element matching the given predicate, or null if no such element was found.
+        val theFirstBatman = batmans.find { actor -> "Michael Keaton".equals(actor) }
+        assertEquals(theFirstBatman, "Michael Keaton")
+    }
+
+    @Test
+    fun whenFilterWithPredicate_thenMatchingItemsAreReturned() {
+        //Returns a list containing only elements matching the given predicate.
+        val theCoolestBatmans = batmans.filter { actor -> actor.contains("a") }
+        assertTrue(theCoolestBatmans.contains("Christian Bale") && theCoolestBatmans.contains("Michael Keaton"))
+    }
+
+    @Test
+    fun whenFilterNotWithPredicate_thenMatchingItemsAreReturned() {
+        //Returns a list containing only elements not matching the given predicate.
+        val theMehBatmans = batmans.filterNot { actor -> actor.contains("a") }
+        assertFalse(theMehBatmans.contains("Christian Bale") && theMehBatmans.contains("Michael Keaton"))
+        assertTrue(theMehBatmans.contains("Ben Affleck") && theMehBatmans.contains("George Clooney"))
+    }
+
+}

core-kotlin-2/src/test/kotlin/com/baeldung/range/CharRangeTest.kt

@@ -0,0 +1,17 @@
+package com.baeldung.range
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class CharRangeTest {
+
+    @Test
+    fun testCharRange() {
+        assertEquals(listOf('a', 'b', 'c'), ('a'..'c').toList())
+    }
+
+    @Test
+    fun testCharDownRange() {
+        assertEquals(listOf('c', 'b', 'a'), ('c'.downTo('a')).toList())
+    }
+}

core-kotlin-2/src/test/kotlin/com/baeldung/range/ColorTest.kt

@@ -0,0 +1,20 @@
+package com.baeldung.range
+
+import org.junit.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class ColorTest {
+
+    @Test
+    fun testEnumRange() {
+
+        println(Color.values().toList());
+        val red = Color.RED
+        val yellow = Color.YELLOW
+        val range = red..yellow
+
+        assertTrue { range.contains(Color.MAGENTA) }
+        assertFalse { range.contains(Color.BLUE) }
+    }
+}

core-kotlin-2/src/test/kotlin/com/baeldung/range/CustomColorTest.kt

@@ -0,0 +1,41 @@
+package com.baeldung.range
+
+import org.junit.Test
+import java.lang.IllegalStateException
+import kotlin.test.assertFailsWith
+import kotlin.test.assertTrue
+
+class CustomColorTest {
+
+    @Test
+    fun testInvalidConstructor(){
+        assertFailsWith(IllegalStateException::class){
+            CustomColor(-1)
+        }
+    }
+
+    @Test
+    fun assertHas10Colors(){
+        assertTrue {
+            val a = CustomColor(1)
+            val b = CustomColor(10)
+            val range = a..b
+            for(cc in range){
+                println(cc)
+            }
+            range.toList().size == 10
+        }
+    }
+
+    @Test
+    fun assertContains0xCCCCCC(){
+        assertTrue {
+            val a = CustomColor(0xBBBBBB)
+            val b = CustomColor(0xDDDDDD)
+            val range = a..b
+            range.contains(CustomColor(0xCCCCCC))
+        }
+    }
+
+}
+

core-kotlin-2/src/test/kotlin/com/baeldung/range/DocumentTest.kt

@@ -0,0 +1,20 @@
+package com.baeldung.range
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+import com.baeldung.jvmannotations.*;
+
+class DocumentTest {
+
+    @Test
+    fun testDefaultMethod() {
+
+        val myDocument = TextDocument()
+        val myTextDocument = XmlDocument(myDocument)
+
+        assertEquals("text", myDocument.getType())
+        assertEquals("text", myTextDocument.getType())
+        assertEquals("document", myTextDocument.getTypeDefault())
+    }
+}

core-kotlin-2/src/test/kotlin/com/baeldung/range/FilterTest.kt

@@ -0,0 +1,24 @@
+package com.baeldung.range
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class FilterTest {
+
+    val r = 1..10
+
+    @Test
+    fun filterTest() {
+        assertEquals(listOf(2, 4, 6, 8, 10), r.filter { it -> it % 2 == 0 }.toList())
+    }
+
+    @Test
+    fun mapTest() {
+        assertEquals(listOf(1, 4, 9, 16, 25, 36, 49, 64, 81, 100), r.map { it -> it * it }.toList())
+    }
+
+    @Test
+    fun reduceTest() {
+        assertEquals(55, r.reduce { a, b -> a + b })
+    }
+}

core-kotlin-2/src/test/kotlin/com/baeldung/range/FirstLastTest.kt

@@ -0,0 +1,22 @@
+package com.baeldung.range
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class FirstLastTest {
+
+    @Test
+    fun testFirst() {
+        assertEquals(1, (1..9).first)
+    }
+
+    @Test
+    fun testLast() {
+        assertEquals(9, (1..9).last)
+    }
+
+    @Test
+    fun testStep() {
+        assertEquals(2, (1..9 step 2).step)
+    }
+}

core-kotlin-2/src/test/kotlin/com/baeldung/range/OtherRangeFunctionsTest.kt

@@ -0,0 +1,40 @@
+package com.baeldung.range
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class OtherRangeFunctionsTest {
+
+    val r = 1..20
+    val repeated = listOf(1, 1, 2, 4, 4, 6, 10)
+
+    @Test
+    fun testMin() {
+        assertEquals(1, r.min())
+    }
+
+    @Test
+    fun testMax() {
+        assertEquals(20, r.max())
+    }
+
+    @Test
+    fun testSum() {
+        assertEquals(210, r.sum())
+    }
+
+    @Test
+    fun testAverage() {
+        assertEquals(10.5, r.average())
+    }
+
+    @Test
+    fun testCount() {
+        assertEquals(20, r.count())
+    }
+
+    @Test
+    fun testDistinct() {
+        assertEquals(listOf(1, 2, 4, 6, 10), repeated.distinct())
+    }
+}

core-kotlin-2/src/test/kotlin/com/baeldung/range/RangeTest.kt

@@ -0,0 +1,22 @@
+package com.baeldung.range
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class RangeTest {
+
+    @Test
+    fun testRange() {
+        assertEquals(listOf(1,2,3), (1.rangeTo(3).toList()))
+    }
+
+    @Test
+    fun testDownTo(){
+        assertEquals(listOf(3,2,1), (3.downTo(1).toList()))
+    }
+
+    @Test
+    fun testUntil(){
+        assertEquals(listOf(1,2), (1.until(3).toList()))
+    }
+}

core-kotlin-2/src/test/kotlin/com/baeldung/range/ReverseRangeTest.kt

@@ -0,0 +1,12 @@
+package com.baeldung.range
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class ReverseRangeTest {
+
+    @Test
+    fun reversedTest() {
+        assertEquals(listOf(9, 6, 3), (1..9).reversed().step(3).toList())
+    }
+}

core-kotlin-2/src/test/kotlin/com/baeldung/range/StepTest.kt

@@ -0,0 +1,17 @@
+package com.baeldung.range
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class StepTest {
+
+    @Test
+    fun testStep() {
+        assertEquals(listOf(1, 3, 5, 7, 9), (1..9 step 2).toList())
+    }
+
+    @Test
+    fun testStepDown() {
+        assertEquals(listOf(9, 7, 5, 3, 1), (9 downTo 1 step 2).toList())
+    }
+}

core-kotlin-2/src/test/kotlin/com/baeldung/range/UntilRangeTest.kt

@@ -0,0 +1,12 @@
+package com.baeldung.range
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class UntilRangeTest {
+
+    @Test
+    fun testUntil() {
+        assertEquals(listOf(1, 2, 3, 4), (1 until 5).toList())
+    }
+}

core-kotlin-2/src/test/kotlin/com/baeldung/scope/ScopeFunctionsUnitTest.kt

@@ -0,0 +1,143 @@
+package com.baeldung.scope
+
+import org.junit.Test
+import kotlin.test.assertTrue
+
+
+class ScopeFunctionsUnitTest {
+
+    class Logger {
+
+        var called : Boolean = false
+
+        fun info(message: String) {
+            called = true
+        }
+
+        fun wasCalled() = called
+    }
+
+    @Test
+    fun shouldTransformWhenLetFunctionUsed() {
+        val stringBuider = StringBuilder()
+        val numberOfCharacters = stringBuider.let {
+            it.append("This is a transformation function.")
+            it.append("It takes a StringBuilder instance and returns the number of characters in the generated String")
+            it.length
+        }
+
+        assertTrue {
+            numberOfCharacters == 128
+        }
+    }
+
+    @Test
+    fun shouldHandleNullabilityWhenLetFunctionUsed() {
+
+        val message: String? = "hello there!"
+        val charactersInMessage = message?.let {
+            "At this point is safe to reference the variable. Let's print the message: $it"
+        } ?: "default value"
+
+        assertTrue {
+            charactersInMessage.equals("At this point is safe to reference the variable. Let's print the message: hello there!")
+        }
+
+        val aNullMessage = null
+        val thisIsNull = aNullMessage?.let {
+            "At this point it would be safe to reference the variable. But it will not really happen because it is null. Let's reference: $it"
+        } ?: "default value"
+
+        assertTrue {
+            thisIsNull.equals("default value")
+        }
+    }
+
+    @Test
+    fun shouldInitializeObjectWhenUsingApply() {
+        val aStudent = Student().apply {
+            studentId = "1234567"
+            name = "Mary"
+            surname = "Smith"
+        }
+
+        assertTrue {
+            aStudent.name.equals("Mary")
+        }
+    }
+
+    @Test
+    fun shouldAllowBuilderStyleObjectDesignWhenApplyUsedInClassMethods() {
+        val teacher = Teacher()
+            .setId(1000)
+            .setName("Martha")
+            .setSurname("Spector")
+
+        assertTrue {
+            teacher.surname.equals("Spector")
+        }
+    }
+
+    @Test
+    fun shouldAllowSideEffectWhenUsingAlso() {
+        val restClient = RestClient("http://www.someurl.com")
+
+        val logger = Logger()
+
+        val headers = restClient
+            .getResponse()
+            .also { logger.info(it.toString()) }
+            .headers
+
+        assertTrue {
+            logger.wasCalled() && headers.headerInfo.equals("some header info")
+        }
+
+    }
+
+    @Test
+    fun shouldInitializeFieldWhenAlsoUsed() {
+        val aStudent = Student().also { it.name = "John"}
+
+        assertTrue {
+            aStudent.name.equals("John")
+        }
+    }
+
+    @Test
+    fun shouldLogicallyGroupObjectCallsWhenUsingWith() {
+        val bankAccount = BankAccount(1000)
+        with (bankAccount) {
+            checkAuthorization("someone")
+            addPayee("some payee")
+            makePayment("payment information")
+        }
+    }
+
+    @Test
+    fun shouldConvertObjectWhenRunUsed() {
+        val stringBuider = StringBuilder()
+        val numberOfCharacters = stringBuider.run {
+            append("This is a transformation function.")
+            append("It takes a StringBuilder instance and returns the number of characters in the generated String")
+            length
+        }
+
+        assertTrue {
+            numberOfCharacters == 128
+        }
+    }
+
+    @Test
+    fun shouldHandleNullabilityWhenRunIsUsed() {
+        val message: String? = "hello there!"
+        val charactersInMessage = message?.run {
+            "At this point is safe to reference the variable. Let's print the message: $this"
+        } ?: "default value"
+
+        assertTrue {
+            charactersInMessage.equals("At this point is safe to reference the variable. Let's print the message: hello there!")
+        }
+    }
+
+}

core-kotlin-2/src/test/kotlin/com/baeldung/splitting/SplittingTest.kt

@@ -0,0 +1,99 @@
+package com.baeldung.lambda
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+
+class SplittingTest {
+    private val evenList = listOf(0, "a", 1, "b", 2, "c");
+
+    private val unevenList = listOf(0, "a", 1, "b", 2, "c", 3);
+
+    private fun verifyList(resultList: List<List<Any>>) {
+        assertEquals("[[0, a], [1, b], [2, c]]", resultList.toString())
+    }
+
+    private fun verifyPartialList(resultList: List<List<Any>>) {
+        assertEquals("[[0, a], [1, b], [2, c], [3]]", resultList.toString())
+    }
+
+    @Test
+    fun whenChunked_thenListIsSplit() {
+        val resultList = evenList.chunked(2)
+        verifyList(resultList)
+    }
+
+    @Test
+    fun whenUnevenChunked_thenListIsSplit() {
+        val resultList = unevenList.chunked(2)
+        verifyPartialList(resultList)
+    }
+
+    @Test
+    fun whenWindowed_thenListIsSplit() {
+        val resultList = evenList.windowed(2, 2)
+        verifyList(resultList)
+    }
+
+    @Test
+    fun whenUnevenPartialWindowed_thenListIsSplit() {
+        val resultList = unevenList.windowed(2, 2, partialWindows = true)
+        verifyPartialList(resultList)
+    }
+
+    @Test
+    fun whenUnevenWindowed_thenListIsSplit() {
+        val resultList = unevenList.windowed(2, 2, partialWindows = false)
+        verifyList(resultList)
+    }
+
+    @Test
+    fun whenGroupByWithAscendingNumbers_thenListIsSplit() {
+        val numberList = listOf(1, 2, 3, 4, 5, 6);
+        val resultList = numberList.groupBy { (it + 1) / 2 }
+        assertEquals("[[1, 2], [3, 4], [5, 6]]", resultList.values.toString())
+        assertEquals("[1, 2, 3]", resultList.keys.toString())
+    }
+
+    @Test
+    fun whenGroupByWithAscendingNumbersUneven_thenListIsSplit() {
+        val numberList = listOf(1, 2, 3, 4, 5, 6, 7);
+        val resultList = numberList.groupBy { (it + 1) / 2 }.values
+        assertEquals("[[1, 2], [3, 4], [5, 6], [7]]", resultList.toString())
+    }
+
+    @Test
+    fun whenGroupByWithRandomNumbers_thenListIsSplitInWrongWay() {
+        val numberList = listOf(1, 3, 8, 20, 23, 30);
+        val resultList = numberList.groupBy { (it + 1) / 2 }
+        assertEquals("[[1], [3], [8], [20], [23], [30]]", resultList.values.toString())
+        assertEquals("[1, 2, 4, 10, 12, 15]", resultList.keys.toString())
+    }
+
+    @Test
+    fun whenWithIndexGroupBy_thenListIsSplit() {
+        val resultList = evenList.withIndex()
+                .groupBy { it.index / 2 }
+                .map { it.value.map { it.value } }
+        verifyList(resultList)
+    }
+
+    @Test
+    fun whenWithIndexGroupByUneven_thenListIsSplit() {
+        val resultList = unevenList.withIndex()
+                .groupBy { it.index / 2 }
+                .map { it.value.map { it.value } }
+        verifyPartialList(resultList)
+    }
+
+    @Test
+    fun whenFoldIndexed_thenListIsSplit() {
+        val resultList = evenList.foldIndexed(ArrayList<ArrayList<Any>>(evenList.size / 2)) { index, acc, item ->
+            if (index % 2 == 0) {
+                acc.add(ArrayList(2))
+            }
+            acc.last().add(item)
+            acc
+        }
+        verifyList(resultList)
+    }
+}

core-kotlin-2/src/test/kotlin/stringcomparison/StringComparisonTest.kt

@@ -0,0 +1,47 @@
+package stringcomparison
+
+import org.junit.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class StringComparisonUnitTest {
+
+    @Test
+    fun `compare using equals operator`() {
+        val first = "kotlin"
+        val second = "kotlin"
+        val firstCapitalized = "KOTLIN"
+        assertTrue { first == second }
+        assertFalse { first == firstCapitalized }
+    }
+
+    @Test
+    fun `compare using referential equals operator`() {
+        val first = "kotlin"
+        val second = "kotlin"
+        val copyOfFirst = buildString { "kotlin" }
+        assertTrue { first === second }
+        assertFalse { first === copyOfFirst }
+    }
+
+    @Test
+    fun `compare using equals method`() {
+        val first = "kotlin"
+        val second = "kotlin"
+        val firstCapitalized = "KOTLIN"
+        assertTrue { first.equals(second) }
+        assertFalse { first.equals(firstCapitalized) }
+        assertTrue { first.equals(firstCapitalized, true) }
+    }
+
+    @Test
+    fun `compare using compare method`() {
+        val first = "kotlin"
+        val second = "kotlin"
+        val firstCapitalized = "KOTLIN"
+        assertTrue { first.compareTo(second) == 0 }
+        assertTrue { first.compareTo(firstCapitalized) == 32 }
+        assertTrue { firstCapitalized.compareTo(first) == -32 }
+        assertTrue { first.compareTo(firstCapitalized, true) == 0 }
+    }
+}

core-kotlin-2/src/test/kotlin/voidtypes/VoidTypesUnitTest.kt

@@ -0,0 +1,63 @@
+package com.baeldung.voidtypes
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+class VoidTypesUnitTest {
+
+    // Un-commenting below methods will result into compilation error
+    // as the syntax used is incorrect and is used for explanation in tutorial.	
+
+    //    fun returnTypeAsVoidAttempt1(): Void {
+    //        println("Trying with Void as return type")
+    //    }
+
+    //    fun returnTypeAsVoidAttempt2(): Void {
+    //        println("Trying with Void as return type")
+    //        return null
+    //    }
+
+    fun returnTypeAsVoidSuccess(): Void? {
+        println("Function can have Void as return type")
+        return null
+    }
+
+    fun unitReturnTypeForNonMeaningfulReturns(): Unit {
+        println("No meaningful return")
+    }
+
+    fun unitReturnTypeIsImplicit() {
+        println("Unit Return type is implicit")
+    }
+
+    fun alwaysThrowException(): Nothing {
+        throw IllegalArgumentException()
+    }
+
+    fun invokeANothingOnlyFunction() {
+        alwaysThrowException()
+
+        var name = "Tom"
+    }
+
+    @Test
+    fun givenJavaVoidFunction_thenMappedToKotlinUnit() {
+        assertTrue(System.out.println() is Unit)
+    }
+
+    @Test
+    fun givenVoidReturnType_thenReturnsNullOnly() {
+        assertNull(returnTypeAsVoidSuccess())
+    }
+
+    @Test
+    fun givenUnitReturnTypeDeclared_thenReturnsOfTypeUnit() {
+        assertTrue(unitReturnTypeForNonMeaningfulReturns() is Unit)
+    }
+
+    @Test
+    fun givenUnitReturnTypeNotDeclared_thenReturnsOfTypeUnit() {
+        assertTrue(unitReturnTypeIsImplicit() is Unit)
+    }
+}

core-kotlin-2/src/test/resources/Kotlin.in

@@ -0,0 +1,5 @@
+Hello to Kotlin. Its:
+1. Concise
+2. Safe
+3. Interoperable
+4. Tool-friendly

core-kotlin-2/src/test/resources/Kotlin.out

@@ -0,0 +1,2 @@
+Kotlin
+Concise, Safe, Interoperable, Tool-friendly