diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 71b5dfa4d..9ccc8fc42 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -52,7 +52,7 @@ jobs:
       uses: actions/checkout@v4
 
     - name: Set up JDK 17
-      uses: actions/setup-java@v3
+      uses: actions/setup-java@v4
       with:
         distribution: 'temurin'
         java-version: '17'
diff --git a/build.gradle.kts b/build.gradle.kts
index dcbe1fdff..bfe377e39 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -1,5 +1,5 @@
 plugins {
-    kotlin("jvm") version "1.9.23"
+    kotlin("jvm") version "2.0.0-RC1"
     jacoco
     id("org.sonarqube") version "5.0.0.4638"
     id("com.diffplug.spotless") version "6.12.0"
@@ -14,7 +14,7 @@ repositories {
 }
 
 dependencies {
-    implementation("org.jetbrains.kotlin:kotlin-stdlib:1.9.23")
+    implementation("org.jetbrains.kotlin:kotlin-stdlib:2.0.0-RC1")
     testImplementation("org.junit.jupiter:junit-jupiter:[5.10.2,)")
     testImplementation("org.hamcrest:hamcrest-core:[2.2,)")
     testImplementation("org.zapodot:embedded-db-junit-jupiter:[2.1.1,)")
@@ -33,7 +33,9 @@ java.sourceCompatibility = JavaVersion.VERSION_11
 java.targetCompatibility = JavaVersion.VERSION_11
 
 tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
-    kotlinOptions.jvmTarget = JavaVersion.VERSION_11.toString()
+    compilerOptions {
+        jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_11)
+    }
 }
 
 publishing {
diff --git a/pom-central.xml b/pom-central.xml
index d20bd4e5b..5e3ab051a 100644
--- a/pom-central.xml
+++ b/pom-central.xml
@@ -27,7 +27,7 @@
         <url>https://github.com/javadev/LeetCode-in-Kotlin</url>
     </scm>
     <properties>
-        <kotlin.version>1.9.23</kotlin.version>
+        <kotlin.version>2.0.0-RC1</kotlin.version>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
     <ciManagement>
@@ -149,6 +149,13 @@
             <version>[5.10.2,)</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <version>[5.10.2,)</version>
+            <scope>test</scope>
+        </dependency>
+
         <dependency>
             <groupId>org.junit.platform</groupId>
             <artifactId>junit-platform-launcher</artifactId>
diff --git a/pom.xml b/pom.xml
index c24e101c4..f20464c83 100644
--- a/pom.xml
+++ b/pom.xml
@@ -26,7 +26,7 @@
         <url>https://github.com/javadev/LeetCode-in-Kotlin</url>
     </scm>
     <properties>
-        <kotlin.version>1.9.23</kotlin.version>
+        <kotlin.version>2.0.0-RC1</kotlin.version>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
     <ciManagement>
@@ -143,6 +143,12 @@
             <version>[5.10.2,)</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <version>[5.10.2,)</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.junit.platform</groupId>
             <artifactId>junit-platform-launcher</artifactId>
diff --git a/src/main/kotlin/g1301_1400/s1396_design_underground_system/UndergroundSystem.kt b/src/main/kotlin/g1301_1400/s1396_design_underground_system/UndergroundSystem.kt
index 5e058ecef..9d21c15e8 100644
--- a/src/main/kotlin/g1301_1400/s1396_design_underground_system/UndergroundSystem.kt
+++ b/src/main/kotlin/g1301_1400/s1396_design_underground_system/UndergroundSystem.kt
@@ -2,13 +2,11 @@ package g1301_1400.s1396_design_underground_system
 
 // #Medium #String #Hash_Table #Design #2023_06_06_Time_703_ms_(99.29%)_Space_76.5_MB_(99.29%)
 
-import java.util.LinkedList
-
 class UndergroundSystem {
     private class StationAndTime(var station: String, var time: Int)
 
     private val averageTimeMap: MutableMap<String, DoubleArray>
-    private val travelerMap: MutableMap<Int, LinkedList<StationAndTime>>
+    private val travelerMap: MutableMap<Int, ArrayList<StationAndTime>>
 
     init {
         averageTimeMap = HashMap()
@@ -16,13 +14,13 @@ class UndergroundSystem {
     }
 
     fun checkIn(id: Int, stationName: String, t: Int) {
-        travelerMap.putIfAbsent(id, LinkedList())
+        travelerMap.putIfAbsent(id, ArrayList())
         travelerMap[id]!!.add(StationAndTime(stationName, t))
     }
 
     fun checkOut(id: Int, stationName: String, t: Int) {
         val list = travelerMap[id]!!
-        val stationAndTime = list.last
+        val stationAndTime = list.last()
         val startToEndStation: String = stationAndTime.station + "->" + stationName
         val duration: Int = t - stationAndTime.time
         if (averageTimeMap.containsKey(startToEndStation)) {
diff --git a/src/main/kotlin/g1401_1500/s1425_constrained_subsequence_sum/Solution.kt b/src/main/kotlin/g1401_1500/s1425_constrained_subsequence_sum/Solution.kt
index ba0ff4796..03166663b 100644
--- a/src/main/kotlin/g1401_1500/s1425_constrained_subsequence_sum/Solution.kt
+++ b/src/main/kotlin/g1401_1500/s1425_constrained_subsequence_sum/Solution.kt
@@ -3,23 +3,21 @@ package g1401_1500.s1425_constrained_subsequence_sum
 // #Hard #Array #Dynamic_Programming #Heap_Priority_Queue #Sliding_Window #Queue #Monotonic_Queue
 // #2023_06_07_Time_649_ms_(33.33%)_Space_51.4_MB_(100.00%)
 
-import java.util.LinkedList
-
 class Solution {
     fun constrainedSubsetSum(nums: IntArray, k: Int): Int {
         val n = nums.size
         var res = Int.MIN_VALUE
-        val mono = LinkedList<IntArray>()
+        val mono = ArrayList<IntArray>()
         for (i in 0 until n) {
             var take = nums[i]
-            while (mono.isNotEmpty() && i - mono.first[0] > k) {
+            while (mono.isNotEmpty() && i - mono.first()[0] > k) {
                 mono.removeFirst()
             }
             if (mono.isNotEmpty()) {
-                val mx = Math.max(0, mono.first[1])
+                val mx = Math.max(0, mono.first()[1])
                 take += mx
             }
-            while (mono.isNotEmpty() && take > mono.last[1]) {
+            while (mono.isNotEmpty() && take > mono.last()[1]) {
                 mono.removeLast()
             }
             mono.add(intArrayOf(i, take))