环境：

scala：2.12.0

java：1.8

spark：3.1.2

一、Idea创建scala项目

Idea新建一个新的项目，选择通过maven创建：

给项目起个名字，设置版本：

maven选项，如果有本地maven的话用本地的，没有的话建议下一个，不行用这个默认的也可以：

设置maven源为aliyun，上面的setting目录创建对应的setting.xml文件：

(base) [~/softwares]$ cat /home/ffzs/.m2/settings.xml 
<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
                          https://maven.apache.org/xsd/settings-1.0.0.xsd">
      <mirrors>
        <mirror>  
            <id>alimaven</id>  
            <name>aliyun maven</name>  
            <url>http://maven.aliyun.com/nexus/content/groups/public/</url>  
            <mirrorOf>central</mirrorOf>          
        </mirror>  
      </mirrors>
</settings>

这里创建的scala项目中默认使用的是scala 2.7.0版本，需要将pom.xml中的版本号换成你是用的版本：

我的改成2.12.12，同时添加spark相关依赖：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.example</groupId>
  <artifactId>untitled</artifactId>
  <version>1.0-SNAPSHOT</version>
  <inceptionYear>2008</inceptionYear>
  <properties>
    <scala.version>2.12.12</scala.version>
  </properties>

  <repositories>
    <repository>
      <id>scala-tools.org</id>
      <name>Scala-Tools Maven2 Repository</name>
      <url>http://scala-tools.org/repo-releases</url>
    </repository>
  </repositories>

  <pluginRepositories>
    <pluginRepository>
      <id>scala-tools.org</id>
      <name>Scala-Tools Maven2 Repository</name>
      <url>http://scala-tools.org/repo-releases</url>
    </pluginRepository>
  </pluginRepositories>

  <dependencies>
    <dependency>
      <groupId>org.scala-lang</groupId>
      <artifactId>scala-library</artifactId>
      <version>${scala.version}</version>
    </dependency>
    <dependency>
      <groupId>org.apache.spark</groupId>
      <artifactId>spark-core_2.12</artifactId>
      <version>3.1.2</version>
    </dependency>
    <dependency>
      <groupId>org.apache.spark</groupId>
      <artifactId>spark-sql_2.12</artifactId>
      <version>3.1.2</version>
    </dependency>
    <dependency>![image-20211004201359161](/home/ffzs/.config/Typora/typora-user-images/image-20211004201359161.png)
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.4</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.specs</groupId>
      <artifactId>specs</artifactId>
      <version>1.2.5</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <sourceDirectory>src/main/scala</sourceDirectory>
    <plugins>
      <plugin>
        <groupId>org.scala-tools</groupId>
        <artifactId>maven-scala-plugin</artifactId>
        <version>2.12</version>
        <executions>
          <execution>
            <goals>
              <goal>compile</goal>
              <goal>testCompile</goal>
            </goals>
          </execution>
        </executions>
        <configuration>
          <scalaVersion>${scala.version}</scalaVersion>
          <args>
            <arg>-target:jvm-1.8</arg>
          </args>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-eclipse-plugin</artifactId>
        <version>2.5.1</version>
        <configuration>
          <downloadSources>true</downloadSources>
          <buildcommands>
            <buildcommand>ch.epfl.lamp.sdt.core.scalabuilder</buildcommand>
          </buildcommands>
          <additionalProjectnatures>
            <projectnature>ch.epfl.lamp.sdt.core.scalanature</projectnature>
          </additionalProjectnatures>
          <classpathContainers>
            <classpathContainer>org.eclipse.jdt.launching.JRE_CONTAINER</classpathContainer>
            <classpathContainer>ch.epfl.lamp.sdt.launching.SCALA_CONTAINER</classpathContainer>
          </classpathContainers>
        </configuration>
      </plugin>
    </plugins>
  </build>
  <reporting>
    <plugins>
      <plugin>
        <groupId>org.scala-tools</groupId>
        <artifactId>maven-scala-plugin</artifactId>
        <configuration>
          <scalaVersion>${scala.version}</scalaVersion>
        </configuration>
      </plugin>
    </plugins>
  </reporting>
</project>

测试：

object RDDGroupTopN {
   def main(args: Array[String]): Unit = {
      //创建SparkConf对象，存储应用程序的配置信息
      val conf = new SparkConf()
      //设置应用程序名称，可以在Spark WebUI中显示
      conf.setAppName("RDDGroupTopN")
      //设置集群Master节点访问地址，此处为本地模式
      conf.setMaster("local[*]")

      val sc = new SparkContext(conf)
      //1. 加载本地数据
      val linesRDD: RDD[String] = sc.textFile("data.txt")

      //2. 将RDD元素转为(String,Int)形式的元组
      val tupleRDD:RDD[(String,Int)]=linesRDD.map(line=>{
         val name=line.split(",")(0)
         val score=line.split(",")(1)
         (name,score.toInt)
      })

      //3. 按照key（姓名）进行分组
      val top5=tupleRDD.groupByKey().map(groupedData=>{
         val name:String=groupedData._1
         //每一组的成绩降序后取前3个
         val scoreTop3:List[Int]=groupedData._2
           .toList.sortWith(_>_).take(3)
         (name,scoreTop3)//返回元组
      })

      //4. 循环打印分组结果
      top5.foreach(tuple=>{
         println("姓名："+tuple._1)
         val tupleValue=tuple._2.iterator
         while (tupleValue.hasNext){
            val value=tupleValue.next()
            println("成绩："+value)
         }
         println("*******************")
      })
   }
}

运行结果：