如何在Scala中为Iterable <object>编写while（）循环？

Question

我正在学习Scala，我想从Java转换一行代码。我在scala中尝试了两种方法，但它们没有用。类ResultScanner来自Apache HBase - ResultScanner，同样适用于Result类

爪哇

for(Result r : resultScanner) System.out.println(r)

Scala

while(resultScanner.hasNext)      // error[1]
  println(resultScanner.next())

//error[1]: value hasNext is not a member of org.apache.hadoop.hbase.client.ResultScanner

我也尝试了以下内容：

resultScanner.foreach(println(_)) // error[2]

// error[2]: value foreach is not a member of org.apache.hadoop.hbase.client.ResultScanner

Answer 1

将Java import scala.collection.JavaConverters._包含在Scala集合可移植性中。然后在集合上调用asScala

resultScanner.asScala foreach println

Answer 2

而不是ArrayList创建ResultScanner并尝试：

scala> import java.util
import java.util

scala> import scala.collection.JavaConversions._
import scala.collection.JavaConversions._

scala> val jList = new util.ArrayList[Int]
jList: java.util.ArrayList[Int] = []

scala> jList.add(2)
res4: Boolean = true

scala> jList.add(6)
res5: Boolean = true

scala> val iterable = iterableAsScalaIterable(jList)
iterable: Iterable[Int] = Wrappers(2, 6)

scala> iterable.foreach(println)
2
6

注意：

选择JavaConverters._而不是JavaConverters._

scala> import scala.collection.JavaConverters._
import scala.collection.JavaConverters._

scala> import java.util
import java.util

scala> val jList = new util.ArrayList[Int]
jList: java.util.ArrayList[Int] = []

scala> jList.add(2)
res0: Boolean = true

scala> jList.add(6)
res1: Boolean = true

scala> val iterable = jList.asScala
iterable: scala.collection.mutable.Buffer[Int] = Buffer(2, 6)

scala> val iterable:Iterable[Int] = jList.asScala
iterable: Iterable[Int] = Buffer(2, 6)