Why do I get java.lang.NoClassDefFoundError when I trying to run this code?

Question

I want to map over the characters in a string, but I'm getting runtime errors.

Example:

object Hello {
    def hello(c: Char) {
        print(c)
    }

    def main(args: Array[String]) {
        "Hello World!".map(hello)
    }
}

Trace:

scalac Hello.scala
java Hello
Exception in thread "main" java.lang.NoClassDefFoundError: scala/LowPriorityImplicits
    at Hello.main(Hello.scala)
Caused by: java.lang.ClassNotFoundException: scala.LowPriorityImplicits
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    ... 1 more
make: *** [test] Error 1

Tibold

It has nothing with mapping, you had problems with your class path. If you running your code with java command, add scala-library.jar to cp -- java doesn't know anything about scala and it's bits. Alternatively run code with scala command. – Dovecote

Run your program with scala Hello instead of java Hello. – Extravagant

Answer 1

I think that your problem is that scala library is not in your runtime classpath. you must manually add manually.

If you are using tools like maven or sbt, maybe the dependency is marked as provided instead compiled.

If you are not using these tools, add "scala-library.jar" to your library directory

Orpington

Answer 2

Also seeing this problem because I don't have the right version of Scala. For those who are using IntelliJ, you can add/change the scala SDK under File > Project Structures > Global Libraries:

If you are compiling and running your project in command line, make sure you have the right version of Scala installed too. e.g.:

Check the Scala version installed:

$ scala -version
Scala code runner version 2.11.8 -- Copyright 2002-2016, LAMP/EPFL

Check the build.sbt to have the right version of Scala:

scalaVersion := "2.11.8"

Germayne

Answer 3

I can confirm the fix is validation dependencies. Or rather what was included by my test library.

For me I upgraded my SpringBoot version which changed my spring-kafka-test version which intern included kafka 2.13.x which finally included scala libs.

I used mvn dependency:tree on my project's build file and searched for '2.12' to find where the old dependency was coming from. Example dependency tree (unrelated dependencies removed). Notice org.apache.kafka:kafka_2.11:jar:0.10.0.0 included as part of my.company.riptide.api:ness-logger:jar:1.0.0 but org.springframework.kafka:spring-kafka-test:jar:2.7.9 includes a newer version org.apache.kafka:kafka_2.13:jar:2.7.2

My solution was to exclude kafaka_2.11 from my ness-logger dependency like this:

<dependency>
  <groupId>my.company.riptide.api</groupId>
  <artifactId>ness-logger</artifactId>
  <version>1.0.0</version>
  <exclusions>
    <exclusion>
      <groupId>org.apache.kafka</groupId>
      <artifactId>kafka_2.11</artifactId>
    </exclusion>
  </exclusions>
</dependency>

Truncated output of mvn dependency:tree:

[INFO] +- my.company.riptide.api:ness-logger:jar:1.0.0:compile
[INFO] |  +- org.springframework.boot:spring-boot-starter-validation:jar:2.5.7:compile
[INFO] |  |  +- org.apache.tomcat.embed:tomcat-embed-el:jar:9.0.55:compile
[INFO] |  |  \- org.hibernate.validator:hibernate-validator:jar:6.2.0.Final:compile
[INFO] |  |     \- jakarta.validation:jakarta.validation-api:jar:2.0.2:compile
[INFO] |  +- commons-io:commons-io:jar:2.7:compile
[INFO] |  +- my.company.eis:ness-logging-package:jar:4.0.1:compile
[INFO] |  |  +- org.apache.avro:avro:jar:1.8.2:compile
[INFO] |  |  |  +- org.codehaus.jackson:jackson-core-asl:jar:1.9.13:compile
[INFO] |  |  |  +- org.codehaus.jackson:jackson-mapper-asl:jar:1.9.13:compile
[INFO] |  |  |  +- com.thoughtworks.paranamer:paranamer:jar:2.7:compile
[INFO] |  |  |  \- org.tukaani:xz:jar:1.5:compile
[INFO] |  |  +- org.apache.avro:avro-compiler:jar:1.8.2:compile
[INFO] |  |  |  +- org.apache.velocity:velocity:jar:1.7:compile
[INFO] |  |  |  \- joda-time:joda-time:jar:2.7:compile
[INFO] |  |  +- org.apache.kafka:kafka_2.11:jar:0.10.0.0:compile
[INFO] |  |  |  +- com.101tec:zkclient:jar:0.8:compile
[INFO] |  |  |  \- org.scala-lang.modules:scala-parser-combinators_2.11:jar:1.0.4:compile
[INFO] |  |  \- com.netflix.hystrix:hystrix-core:jar:1.5.18:compile
[INFO] |  |     +- com.netflix.archaius:archaius-core:jar:0.4.1:compile
[INFO] |  |     \- io.reactivex:rxjava:jar:1.3.8:compile
[INFO] |  +- org.springframework.boot:spring-boot-loader-tools:jar:2.5.7:compile
[INFO] |  |  \- org.apache.commons:commons-compress:jar:1.21:compile
[INFO] |  \- my.company.riptide.springboot:graceful-shutdown:jar:1.0.2:compile

[INFO] +- org.springframework.kafka:spring-kafka:jar:2.7.9:compile
[INFO] |  +- org.springframework:spring-messaging:jar:5.3.13:compile
[INFO] |  +- org.springframework:spring-tx:jar:5.3.13:compile
[INFO] |  +- org.springframework.retry:spring-retry:jar:1.3.1:compile
[INFO] |  |  \- javax.annotation:javax.annotation-api:jar:1.3.2:compile
[INFO] |  +- org.apache.kafka:kafka-clients:jar:2.7.2:compile
[INFO] |  |  +- com.github.luben:zstd-jni:jar:1.4.5-6:compile
[INFO] |  |  +- org.lz4:lz4-java:jar:1.7.1:compile
[INFO] |  |  \- org.xerial.snappy:snappy-java:jar:1.1.7.7:compile
[INFO] |  \- com.google.code.findbugs:jsr305:jar:3.0.2:compile
[INFO] +- junit:junit:jar:4.13.2:test
[INFO] |  \- org.hamcrest:hamcrest-core:jar:2.2:compile
[INFO] +- io.cucumber:cucumber-spring:jar:7.0.0:test
[INFO] |  \- org.apiguardian:apiguardian-api:jar:1.1.2:test
[INFO] +- io.cucumber:cucumber-core:jar:7.0.0:test
[INFO] |  +- io.cucumber:cucumber-gherkin:jar:7.0.0:test
[INFO] |  +- io.cucumber:cucumber-gherkin-messages:jar:7.0.0:test
[INFO] |  +- io.cucumber:messages:jar:17.1.1:test
[INFO] |  +- io.cucumber:tag-expressions:jar:4.0.2:test
[INFO] |  +- io.cucumber:cucumber-expressions:jar:13.0.1:test
[INFO] |  +- io.cucumber:datatable:jar:7.0.0:test
[INFO] |  +- io.cucumber:cucumber-plugin:jar:7.0.0:test
[INFO] |  +- io.cucumber:docstring:jar:7.0.0:test
[INFO] |  +- io.cucumber:html-formatter:jar:17.0.0:test
[INFO] |  \- io.cucumber:create-meta:jar:6.0.1:test

[INFO] +- org.springframework.kafka:spring-kafka-test:jar:2.7.9:test
[INFO] |  +- org.apache.kafka:kafka-clients:jar:test:2.7.2:test
[INFO] |  +- org.apache.kafka:kafka-streams:jar:2.7.2:test
[INFO] |  |  +- org.apache.kafka:connect-json:jar:2.7.2:test
[INFO] |  |  |  \- org.apache.kafka:connect-api:jar:2.7.2:test
[INFO] |  |  \- org.rocksdb:rocksdbjni:jar:5.18.4:test
[INFO] |  +- org.apache.kafka:kafka-streams-test-utils:jar:2.7.2:test
[INFO] |  +- org.apache.kafka:kafka_2.13:jar:2.7.2:test
[INFO] |  |  +- org.apache.kafka:kafka-raft:jar:2.7.2:test
[INFO] |  |  +- com.fasterxml.jackson.module:jackson-module-scala_2.13:jar:2.12.5:test
[INFO] |  |  +- com.fasterxml.jackson.dataformat:jackson-dataformat-csv:jar:2.12.5:test
[INFO] |  |  +- net.sf.jopt-simple:jopt-simple:jar:5.0.4:compile
[INFO] |  |  +- com.yammer.metrics:metrics-core:jar:2.2.0:compile
[INFO] |  |  +- org.scala-lang.modules:scala-collection-compat_2.13:jar:2.2.0:test
[INFO] |  |  +- org.scala-lang.modules:scala-java8-compat_2.13:jar:0.9.1:test
[INFO] |  |  +- org.scala-lang:scala-library:jar:2.13.3:compile
[INFO] |  |  +- org.scala-lang:scala-reflect:jar:2.13.3:test
[INFO] |  |  +- com.typesafe.scala-logging:scala-logging_2.13:jar:3.9.2:test
[INFO] |  |  +- org.apache.zookeeper:zookeeper:jar:3.5.9:compile
[INFO] |  |  |  +- org.apache.zookeeper:zookeeper-jute:jar:3.5.9:compile
[INFO] |  |  |  +- org.apache.yetus:audience-annotations:jar:0.5.0:compile
[INFO] |  |  |  \- io.netty:netty-transport-native-epoll:jar:4.1.70.Final:compile
[INFO] |  |  \- commons-cli:commons-cli:jar:1.4:test
[INFO] |  +- org.apache.kafka:kafka_2.13:jar:test:2.7.2:test
[INFO] |  \- org.junit.jupiter:junit-jupiter-api:jar:5.7.2:test
[INFO] |     +- org.opentest4j:opentest4j:jar:1.2.0:test
[INFO] |     \- org.junit.platform:junit-platform-commons:jar:1.7.2:test

Aniseed