Update Gradle and Kotlin

build.gradle

@@ -1,13 +1,13 @@
 buildscript {
-    ext.kotlin_version = '1.3.21'
+    ext.kotlin_version = '2.0.0'
 
     repositories {
         mavenCentral()
         jcenter()
     }
     dependencies {
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-        classpath 'com.vanniktech:gradle-maven-publish-plugin:0.8.0'
+        classpath 'com.vanniktech:gradle-maven-publish-plugin:0.29.0'
     }
 }
 
@@ -22,17 +22,10 @@ repositories {
 }
 
 dependencies {
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
+    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
 
     testImplementation 'junit:junit:4.12'
     testImplementation 'com.nhaarman.mockitokotlin2:mockito-kotlin:2.1.0'
     testImplementation "org.jetbrains.kotlin:kotlin-reflect:$kotlin_version"
-    testImplementation 'org.assertj:assertj-core:3.11.1'
-}
-
-compileKotlin {
-    kotlinOptions.jvmTarget = JavaVersion.VERSION_1_8
-}
-compileTestKotlin {
-    kotlinOptions.jvmTarget = JavaVersion.VERSION_1_8
+    testImplementation "com.google.truth:truth:1.4.4"
 }

gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.3.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.9-all.zip

src/main/kotlin/com/tinder/StateMachine.kt

@@ -6,7 +6,7 @@ class StateMachine<STATE : Any, EVENT : Any, SIDE_EFFECT : Any> private construc
     private val graph: Graph<STATE, EVENT, SIDE_EFFECT>
 ) {
 
-    private val stateRef = AtomicReference<STATE>(graph.initialState)
+    private val stateRef = AtomicReference(graph.initialState)
 
     val state: STATE
         get() = stateRef.get()