val files = new File("data").list()
val filtered = files.filter(name => name.contains("txn"))
val masterList = new ListBuffer[String]
for (file <- filtered) {
val lines = Source.fromFile(new File("data\\" + file), "UTF-16").getLines
val cleaned = lines.filter(!masterList.contains(_))
println("*" + cleaned.length)
cleaned.foreach(println(_))
println("**" + cleaned.length)
cleaned.foreach(masterList.append(_))
}
代码的输出如下
*175
**0
我不明白为什么我的列表消失了
cleaned是一个迭代器。
scala> val cleaned = lines.filter(_!="")
cleaned: Iterator[String] = non-empty iterator
分配后立即非空。 scala 中的迭代器是一次性的 - 一旦你遍历它（例如通过应用length方法）它变成空：
scala> cleaned.length
res0: Int = 13
scala> cleaned.length
res1: Int = 0
您可以通过转换为 List 或 Seq （惰性）来修复该行为：
scala> val lines=Source.fromFile("bla.txt").getLines
lines: Iterator[String] = non-empty iterator
scala> val cleaned = lines.filter(_!="").toSeq
cleaned: Seq[String] = Stream(first, ?)
scala> cleaned.length
res4: Int = 13
scala> cleaned.length
res5: Int = 13
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