各种版本 WordCount

1 hadoop的MapReduce版

①mapper类

//KEYIN 输入数据的key
//VALUEIN 输入数据的value
//KEYOUT 输出数据的key
//VALUEOUT 输出数据的value
public class WordCountMapper extends Mapper<LongWritable, Text, Text, IntWritable>{
    private Text k = new Text();
    private IntWritable v = new IntWritable(1);

    @Override
    protected void map(LongWritable key, Text value, Context context)
            throws IOException, InterruptedException {
        //1.一行单词
        String[] words = value.toString().split(" ");
        //2.循环写出
        for (String word : words) {
            k.set(word);
            context.write(k, v);
        }
    }
}

②reducer类

//KEYIN VALUEIN map阶段输出的key和value
public class WordCountReducer extends Reducer<Text, IntWritable, Text, IntWritable>{
    private IntWritable v = new IntWritable();

    @Override
    protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
        //1.累加求和 
        int sum = 0;
        for (IntWritable value : values) {
            sum += value.get();
        }
        
        //2.写出
        v.set(sum);
        context.write(key, v);
    }
}

③driver类

public class WordCountDriver {

    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration conf = new Configuration();
        //1.获取Job对象
        Job job = Job.getInstance(conf );
        
        //2.设置Jar存储位置
        job.setJarByClass(WordCountDriver.class);
        
        //3.关联Mapper和Reducer类
        job.setMapperClass(WordCountMapper.class);
        job.setReducerClass(WordCountReducer.class);
        
        //4.设置map阶段输出数据的key和value类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);
        
        //5.设置最终数据输出的key和value类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        
        //6.设置输入路径和输出路径
        FileInputFormat.setInputPaths(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        
        //7.提交Job
        boolean result = job.waitForCompletion(true);
        
        System.exit(result ? 0 : 1);
    }

}

运行时须指定输入输出路径

2 Java8 Stream版

public static void main(String[] args) throws ParseException {
    ArrayList<String> list = new ArrayList<>();
    list.add("scala hadoop linux scala");
    list.add("word hello world hadoop spark");
    list.add("hello world spark scala");

    Map<String, Long> result = list.stream()
            .flatMap(str -> Arrays.stream(str.split(" ")))
            .collect(Collectors.groupingBy(
                    Function.identity() //按照单词自身分组
                    , Collectors.counting()) //分组后直接count
            );

    System.out.println(result); //{world=2, spark=2, scala=3, linux=1, hello=2, hadoop=2, word=1}

}

3 scala原始版

def main(args: Array[String]): Unit = {
  //word count
  val lines = List[String]("scala hadoop linux scala","word hello world hadoop spark","hello world spark scala")

  //空格切割扁平化
  val res1: immutable.Seq[String] = lines.flatMap(_.split(" "))
  println(res1) //List(scala, hadoop, linux, scala, word, hello, world, hadoop, spark, hello, world, spark, scala)

  //映射成元组
  val res2: immutable.Seq[(String, Int)] = res1.map((_, 1))
  println(res2) //List((scala,1), (hadoop,1), (linux,1), (scala,1), (word,1), (hello,1), (world,1), (hadoop,1), (spark,1), (hello,1), (world,1), (spark,1), (scala,1))

  //将上一步的元组分组
  val res3: Map[String, immutable.Seq[(String, Int)]] = res2.groupBy(_._1)
  println(res3) //Map(world -> List((world,1), (world,1)), hadoop -> List((hadoop,1), (hadoop,1)), spark -> List((spark,1), (spark,1)), scala -> List((scala,1), (scala,1), (scala,1)), linux -> List((linux,1)), hello -> List((hello,1), (hello,1)), word -> List((word,1)))

  //value的长度就是单词的个数
  val res4: Map[String, Int] = res3.map(x => (x._1, x._2.size))
  println(res4) //Map(world -> 2, hadoop -> 2, spark -> 2, scala -> 3, linux -> 1, hello -> 2, word -> 1)

  //倒序展示
  val res = res4.toList.sortBy(_._2).reverse
  println(res) //List((scala,3), (hello,2), (spark,2), (hadoop,2), (world,2), (word,1), (linux,1))

}

　　

4 spark版

单词文件

Hello Scala
Hello Spark
Hello BigData
Hadoop Yarn Scala Java

代码

def main(args: Array[String]): Unit = {

  val conf = new SparkConf().setMaster("local[*]").setAppName("word count")
  val sc = new SparkContext(conf)

  //从文件生成RDD
  val rdd = sc.textFile("input/word.txt")

  //切割扁平化
  val flatMapRDD: RDD[String] = rdd.flatMap(_.split(" "))

  //映射成元组
  val mapRDD: RDD[(String, Int)] = flatMapRDD.map((_, 1))

  //按照key进行聚合
  val reduceByKeyRDD: RDD[(String, Int)] = mapRDD.reduceByKey(_ + _)

  //倒序展示
  reduceByKeyRDD.sortBy(_._2,false).collect().foreach(println)
  //(Hello,3)
  //(Scala,2)
  //(Yarn,1)
  //(Java,1)
  //(BigData,1)
  //(Spark,1)
  //(Hadoop,1)

}