scala.MatchError : [Ljava. lang.String; (类 [Ljava.lang.String;)

Question

当我想读取文件时，我的文件格式是:
12334 本:23，字:21，老师:23

   val fp = "/user/user_id.txt"
   sc.textFile(fp).map { s =>
   val Array(did, info_s) = s.split("\t")
   val info = info_s.split(",").map { kv =>
      val Array(k, v) = kv.split(":")
      (k, v.toDouble)
    }.toSeq
    (did, info)
  }

这个scala错误出现了。这是怎么发生的？

scala.MatchError: [Ljava.lang.String;@51443799 (of class [Ljava.lang.String;)
at com.test.news.IO$$anonfun$1.apply(App.scala:58)
at com.test.news.IO$$anonfun$1.apply(App.scala:57)
at scala.collection.Iterator$$anon$11.next(Iterator.scala:409)
at scala.collection.Iterator$class.foreach(Iterator.scala:893)
at scala.collection.AbstractIterator.foreach(Iterator.scala:1336)
at scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:59)
at scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:104)
at scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:48)
at scala.collection.TraversableOnce$class.to(TraversableOnce.scala:310)
at scala.collection.AbstractIterator.to(Iterator.scala:1336)
at scala.collection.TraversableOnce$class.toBuffer(TraversableOnce.scala:302)
at scala.collection.AbstractIterator.toBuffer(Iterator.scala:1336)
at scala.collection.TraversableOnce$class.toArray(TraversableOnce.scala:289)
at scala.collection.AbstractIterator.toArray(Iterator.scala:1336)
at org.apache.spark.rdd.RDD$$anonfun$collect$1$$anonfun$13.apply(RDD.scala:912)
at org.apache.spark.rdd.RDD$$anonfun$collect$1$$anonfun$13.apply(RDD.scala:912)
at org.apache.spark.SparkContext$$anonfun$runJob$5.apply(SparkContext.scala:1916)
at org.apache.spark.SparkContext$$anonfun$runJob$5.apply(SparkContext.scala:1916)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:70)
at org.apache.spark.scheduler.Task.run(Task.scala:86)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:274)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

第 58 行是 val Array(did, info_s) = s.split("\t") ，我不能用这种方式吗？我很困惑~求助!

Answer 1

您在第 5 行 ( val Array(k, v) = ... ) 的语法使用数组 unapply method .如果您在提取器中提供的绑定(bind)数量不等于数组的长度，则会出现匹配错误:

scala> val Array(k, v) = "1,2".split(",")
k: String = 1
v: String = 2

scala> val Array(k, v) = "1,2,3".split(",")
scala.MatchError: [Ljava.lang.String;@508dec2b (of class [Ljava.lang.String;)

在您的情况下，这可能是由格式错误的输入(多个 : 或无)引起的。虽然提取器有用且简洁，但它们的错误消息很隐晦，因此如果您不确定匹配是否正确(例如读取任意文本文件)，最好使用稍微冗长的语法:

val (k, v) = kv.split(":") match {
  case Array(f1, f2) => (f1, f2)
  case Array(elems) => fatal("found invalid K/V pair: expected 2 elements, found ${elems.length}")
}