spark submit Error: Failed to load class FirstDemo

Question

I create sbt project with Intellij and build Artifacts to jar file. I put jar file to server and submit, but I got this error:

this is my code :-

import org.apache.spark.{SparkConf,SparkContext}
object FirstDemoo {
  def main(args: Array[String]): Unit = {
    val conf=new SparkConf().setMaster("local[*]").setAppName("FirstDemo")
    val sc=new SparkContext(conf)
    val rdd=sc.parallelize(Array(5,10,30))
    println(rdd.reduce(_+_))
  }
}

here is my build.sbt file:-

name := "DemooSpark"

version := "0.1"

scalaVersion := "2.12.6"

// https://mvnrepository.com/artifact/org.apache.spark/spark-core
libraryDependencies += "org.apache.spark" %% "spark-core" % "3.2.0"

// https://mvnrepository.com/artifact/org.apache.spark/spark-sql
libraryDependencies += "org.apache.spark" %% "spark-sql" % "3.2.0"

when running spark-submit it is showing error saying:

spark-submit --class FirstDemoo /home/hduser/IdeaProjects/DemooSpark/out/artifacts/DemooSpark_jar2/DemooSpark.jar
22/03/11 14:22:24 WARN Utils: Your hostname, kuldeep-VirtualBox resolves to a loopback address: 127.0.0.1; using 10.0.2.15 instead (on interface enp0s3)
22/03/11 14:22:24 WARN Utils: Set SPARK_LOCAL_IP if you need to bind to another address
Error: Failed to load class FirstDemoo.
log4j:WARN No appenders could be found for logger (org.apache.spark.util.ShutdownHookManager).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.