import org.apache.spark
import org.apache.spark.rdd.RDD

class HelloWorldDemo {
  def main(args: Array[String]): Unit = {
    val rootPath: String = _
    val file: String = s"${rootPath}/wikiOfSpark.txt"

    // 读取文件内容
//   fixme oldAPI : val lineRDD: RDD[String] = spark.sparkContext.textFile(file)
    val lineRDD: RDD[String] = spark.SparkContext.getOrCreate().textFile(file)

    // 以行为单位做分词
    val wordRDD: RDD[String] = lineRDD.flatMap(line => line.split(" "))
    val cleanWordRDD: RDD[String] = wordRDD.filter(word => !word.equals(""))
    // 把RDD元素转换为（Key，Value）的形式
    val kvRDD: RDD[(String, Int)] = cleanWordRDD.map(word => (word, 1))
    // 按照单词做分组计数
    val wordCounts: RDD[(String, Int)] = kvRDD.reduceByKey((x, y) => x + y)
    // 打印词频最高的5个词汇
    wordCounts.map{case (k, v) => (v, k)}.sortByKey(false).take(5)
  }
}