在Scala中迭代Java集合 [英] Iterating over Java collections in Scala

问题描述

我正在撰写一些使用 Apache POI API的Scala代码。我想迭代包含在 java.util.Iterator 中的行，我从Sheet类中获取。我想在中为每个样式循环使用迭代器，所以我一直试图将其转换为原生Scala集合，但不会运气。

I'm writing some Scala code which uses the Apache POI API. I would like to iterate over the rows contained in the java.util.Iterator that I get from the Sheet class. I would like to use the iterator in a for each style loop, so I have been trying to convert it to a native Scala collection but will no luck.

我看过Scala包装类/ traits，但我看不出如何正确使用它们。如何在Scala中迭代Java集合而不使用详细的 while（hasNext（））getNext（）循环风格？

I have looked at the Scala wrapper classes/traits, but I can not see how to use them correctly. How do I iterate over a Java collection in Scala without using the verbose while(hasNext()) getNext() style of loop?

这是我基于正确答案写的代码：

Here's the code I wrote based on the correct answer:

class IteratorWrapper[A](iter:java.util.Iterator[A])
{
    def foreach(f: A => Unit): Unit = {
        while(iter.hasNext){
          f(iter.next)
        }
    }
}

object SpreadsheetParser extends Application
{
    implicit def iteratorToWrapper[T](iter:java.util.Iterator[T]):IteratorWrapper[T] = new IteratorWrapper[T](iter)

    override def main(args:Array[String]):Unit =
    {
        val ios = new FileInputStream("assets/data.xls")
        val workbook = new HSSFWorkbook(ios)
        var sheet = workbook.getSheetAt(0)
        var rows = sheet.rowIterator()

        for (val row <- rows){
            println(row)
        }
    }
}

推荐答案

有一个包装类（ scala.collection.jcl.MutableIterator .Wrapper ）。所以如果你定义

There is a wrapper class (scala.collection.jcl.MutableIterator.Wrapper). So if you define

implicit def javaIteratorToScalaIterator[A](it : java.util.Iterator[A]) = new Wrapper(it)

那么它将作为Scala迭代器的子类，所以你可以做 foreach 。

then it will act as a sub class of the Scala iterator so you can do foreach.

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