Spark運算元：RDD行動Action操作學習–countByKey、foreach、sortBy

package chen

import org.apache.spark._

object rdd_test {

    System.setProperty ("hadoop.home.dir", "C:\\hadoop_home\\")
    def main(args: Array[String]) {


        /*
         *   countByKey  for  foreach sortBy 學習
         *
        */

        val sparkConf = new SparkConf().setMaster("local").setAppName("rdd")
        val sc = new SparkContext(sparkConf)

        val rdd1 = sc.makeRDD(Array(("A", 0), ("A", 2), ("B", 1), ("B", 2), ("B", 3)))
        rdd1.foreach(println(_))
        /*
        (A,0)
        (A,2)
        (B,1)
        (B,2)
        (B,3)
        */

        for (elem <- rdd1.countByKey) {
            println(elem)
        }
        /*
        (B,3)
        (A,2)
        */

        var cnt = sc.accumulator(0)
        val rdd2 = sc.makeRDD(1 to 10,2)
        rdd2.foreach(println(_))         //輸出： 1 2 3 4 5 6 7 8 9 10
        rdd2.foreach(x => cnt += x)
        println(cnt) //55


        val rdd3 = sc.makeRDD(Seq(3,6,7,1,2,0),2)
        rdd3.sortBy(x => x).collect.foreach(println(_))       //    0, 1, 2, 3, 6, 7   預設升序

        rdd3.sortBy(x => x, false).collect.foreach(println(_)) //     7, 6, 3, 2, 1, 0  降序

        //RDD[K,V]型別
        //按照kye來排序
        rdd1.sortBy(x=>x).collect().foreach(println(_))

        //按照value的升序排列，false就降序
        rdd1.sortBy(x=>x._2, true).collect().foreach(println(_))
        /*
        (A,0)
        (B,1)
        (A,2)
        (B,2)
        (B,3)
        */

    }
}