key出现的次数
package com.atguigu
import org.apache.spark.rdd.RDD
import org.apache.spark.{SparkConf, SparkContext}
object Action {
def main(args: Array[String]): Unit = {
val conf: SparkConf = new SparkConf().setMaster("local[*]").setAppName("ADCount")
val sc = new SparkContext(conf)
val rdd: RDD[(String, Int)] = sc.makeRDD(List(("a",1),("b",2),("a",3),("b",4),("a",5)))
val stringToLong: collection.Map[String, Long] = rdd.countByKey()
println(stringToLong)
}
}
Map(a -> 3, b -> 2)
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