user_artist__data数据记录用户播放某首歌曲的次数，数据包含3个字段，分别为useid(用户ID)、artistid(艺术家ID)、playcount(播放次数)更新一下子

package thisterm;
import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.SparkSession;
public class homework_4 {
  public static void main(String[] args) {
  // TODO Auto-generated method stub
  SparkSession spark = SparkSession.builder().master("local").appName("Java Spark SQL basic example").config("spark.testing.memory","2147480000").getOrCreate();
  Dataset<Row> df = spark.read().format("csv").option("header", "true").load("file:///home/gyq/eclipse-workspace/user_artist_data.csv");
  //df.show();
  df.createOrReplaceTempView("UAD");
  //1）统计非重复的用户个数。
  //spark.sql("select count(distinct userid) as usernumber from UAD ").show();
  //统计用户听过的歌曲总数。
  //spark.sql("select userid,count(playcount) as playcount from UAD group by userid").show();
//  找出ID为“1000002”的用户最喜欢的10首歌曲（即播放次数最多的10首歌曲）。
  spark.sql("select * from UAD where userid='1000002' order by playcount desc limit 20").show();
  spark.stop();
  }
}

package thisterm;
import java.io.Serializable;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.SparkSession;
public class addtableheader {
  public static class Person implements Serializable {
     private String userid;
     private String artistid;
     private int playcount;
     public String getUserid() {return userid;  }
     public void setUserid(String userid) {  this.userid = userid; }
     public String getArtistid() {return artistid;}
     public void setArtistid(String artistid) {this.artistid = artistid;} 
     public int getPlaycount() {return playcount;}
     public void setPlaycount(int playcount) {this.playcount = playcount;}
  }
  public static void main(String[] args) {
  // TODO Auto-generated method stub
  SparkSession spark = SparkSession.builder().master("local").appName("Java Spark SQL basic example").config("spark.testing.memory","2147480000").getOrCreate();
  JavaRDD<String> stringRDD = spark.read()
         .textFile("/home/gyq/eclipse-workspace/user_artist_data.csv")
         .javaRDD();
  JavaRDD<Person> peopleRDD = stringRDD.map(line -> {
         String[] parts = line.split(" ");
         Person person = new Person();
         person.setUserid(parts[0]);
         person.setArtistid(parts[1]);
         person.setPlaycount(Integer.parseInt(parts[2]));
         return person;
       });
  Dataset<Row> peopleDF = spark.createDataFrame(peopleRDD, Person.class);
  //peopleDF.show();
  peopleDF.createOrReplaceTempView("UAD");
  //1）统计非重复的用户个数。
    spark.sql("select count(distinct userid) as usernumber from UAD ").show();
  //统计用户听过的歌曲总数。
    //spark.sql("select userid,count(playcount) as playcount from UAD group by userid").show();
//  找出ID为“1000002”的用户最喜欢的10首歌曲（即播放次数最多的10首歌曲）。
  //spark.sql("select * from UAD where userid='1000002' order by playcount desc limit 10").show();
  }
}