spark--Actions算子--countByKey

import org.apache.log4j.{Level, Logger}import org.apache.spark.{SparkConf, SparkContext}/**  * Created by liupeng on 2017/6/17.  */object A_countByKey {  System.setProperty("hadoop.home.dir","F:\\hadoop-2.6.5")  Logger.getLogger("org").setLevel(Level.ERROR)  def main(args: Array[String]): Unit = {    val conf = new SparkConf().setAppName("countByKey_test").setMaster("local")    val sc = new SparkContext(conf)    //准备一下数据    val nameList = List(("A",1),("A",2),("B",1))    val data = sc.parallelize(nameList)    //仅适用于类型（K，V）的RDD,返回与每个键的计数的（K，Int）对的hashmap    val num = data.countByKey()    for (x <- num) {      println(x)    }  }}

运行结果：

(B,1)
(A,2)