Migrate to Gradle Kotlin DSL

build.gradle.kts

@@ -0,0 +1,20 @@
+plugins {
+    kotlin("jvm") version "1.3.21"
+}
+
+repositories {
+    mavenCentral()
+}
+
+sourceSets["main"].java.srcDir("src")
+sourceSets["test"].java.srcDir("test")
+
+dependencies {
+    implementation(kotlin("stdlib"))
+    implementation("com.google.guava:guava:27.0.1-jre")
+    testImplementation("org.junit.jupiter:junit-jupiter:5.4.0")
+}
+
+tasks.withType<Test> {
+    useJUnitPlatform()
+}