在IDEA中使用Java编写WordCount程序

创建项目详细过程请参考博客：
在IDEA中用Scala编写WordCount程序并且上传到集群中运行
https://blog.csdn.net/weixin_43866709/article/details/88599701

下面是代码：

package cn.edu360.spark;


import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaPairRDD;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.api.java.function.FlatMapFunction;
import org.apache.spark.api.java.function.Function2;
import org.apache.spark.api.java.function.PairFunction;
import scala.Tuple2;


import java.util.Arrays;
import java.util.Iterator;

public class javaWordCount {
    public static void main(String[] args){
        SparkConf conf = new SparkConf().setAppName("javaWordCount");
        //创建sparkContext
        JavaSparkContext jsc = new JavaSparkContext(conf);
        //指定以后从哪里读取数据
        JavaRDD<String> lines = jsc.textFile(args[0]);
        //切分压平
        JavaRDD<String> words = lines.flatMap(new FlatMapFunction<String, String>() {
            @Override
            public Iterator<String> call(String line) throws Exception {
                return Arrays.asList(line.split(" ")).iterator();
            }
        });
    //将单词和1组合在一起
    JavaPairRDD<String, Integer> wordAndOne = words.mapToPair(new PairFunction<String, String, Integer>() {
        @Override
        public Tuple2<String, Integer> call(String word) throws Exception {
            return new Tuple2<>(word, 1);
        }
    });

    //聚合
    JavaPairRDD<String, Integer> reduced = wordAndOne.reduceByKey(new Function2<Integer, Integer, Integer>() {
        @Override
        public Integer call(Integer v1, Integer v2) throws Exception {
            return v1 + v2;
        }
    });

    //调换key和value顺序
    JavaPairRDD<Integer, String> swaped = reduced.mapToPair(new PairFunction<Tuple2<String, Integer>, Integer, String>() {
        @Override
        public Tuple2<Integer, String> call(Tuple2<String, Integer> tp) throws Exception {
            //return new Tuple2<>(tp._2,tp._1);
            return tp.swap();
        }
    });

    //排序
    JavaPairRDD<Integer, String> sorted = swaped.sortByKey(false);

    //调整顺序
    JavaPairRDD<String, Integer> result = sorted.mapToPair(new PairFunction<Tuple2<Integer, String>, String, Integer>() {
        @Override
        public Tuple2<String, Integer> call(Tuple2<Integer, String> tp) throws Exception {
            return tp.swap();
        }
    });

    //将数据保存到hdfs
    result.saveAsTextFile(args[1]);

    //释放资源
    jsc.stop();

    }

}

然后打成jar包，上传到spark集群运行。
运行命令是：

spark-submit //向spark集群提交任务命令
–master spark://L1:7077 // --master指定spark集群上的master主机和端口
–class com.baidu.spark.javaWordCount //指定程序的类名（程序执行的入口）
/home/hadoop/original-SparkTest1-1.0-SNAPSHOT-java.jar//指定jar 包的位置
hdfs://L1:9000/aaa //指定HDFS上namenode 的主机名和端口，以及文件位置
hdfs://L1:9000/aaajavaout //指定程序运行结果存放位置