java conversion_在Scala中JavaConverters和JavaConversions有什么区别？

JavaConversions提供了一系列隐式方法，可以在Java集合和最接近的对应Scala集合之间进行转换，反之亦然。这是通过创建包装器来实现的，它实现了Scala接口并将调用转发到底层Java集合或Java接口，将调用转发到底层Scala集合。

JavaConverters使用pimp-my-library模式将asScala方法“添加”到Java集合中，并将asJava方法“添加”到Scala集合中，该集合返回上面讨论的适当的包装器。它比JavaConversions(从2.8版本)更新(从2.8.1版本开始)，并使Scala和Java集合之间的转换显式。与大卫在他的答案中写的相反，我建议你使用JavaConverters的习惯，因为你不太可能编写代码，使很多隐式转换，因为你可以控制唯一的地方，发生：你写.asScala或.asJava。

这里是JavaConverters提供的转换方法：

Pimped Type | Conversion Method | Returned Type

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scala.collection.Iterator | asJava | java.util.Iterator

scala.collection.Iterator | asJavaEnumeration | java.util.Enumeration

scala.collection.Iterable | asJava | java.lang.Iterable

scala.collection.Iterable | asJavaCollection | java.util.Collection

scala.collection.mutable.Buffer | asJava | java.util.List

scala.collection.mutable.Seq | asJava | java.util.List

scala.collection.Seq | asJava | java.util.List

scala.collection.mutable.Set | asJava | java.util.Set

scala.collection.Set | asJava | java.util.Set

scala.collection.mutable.Map | asJava | java.util.Map

scala.collection.Map | asJava | java.util.Map

scala.collection.mutable.Map | asJavaDictionary | java.util.Dictionary

scala.collection.mutable.ConcurrentMap | asJavaConcurrentMap | java.util.concurrent.ConcurrentMap

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java.util.Iterator | asScala | scala.collection.Iterator

java.util.Enumeration | asScala | scala.collection.Iterator

java.lang.Iterable | asScala | scala.collection.Iterable

java.util.Collection | asScala | scala.collection.Iterable

java.util.List | asScala | scala.collection.mutable.Buffer

java.util.Set | asScala | scala.collection.mutable.Set

java.util.Map | asScala | scala.collection.mutable.Map

java.util.concurrent.ConcurrentMap | asScala | scala.collection.mutable.ConcurrentMap

java.util.Dictionary | asScala | scala.collection.mutable.Map

java.util.Properties | asScala | scala.collection.mutable.Map[String, String]

要直接使用Java的转换，你最好直接从JavaConversions调用方法;例如。：

List javaList = new ArrayList(Arrays.asList("a", "b", "c"));

System.out.println(javaList); // [a, b, c]

Buffer scalaBuffer = JavaConversions.asScalaBuffer(javaList);

System.out.println(scalaBuffer); // Buffer(a, b, c)

List javaListAgain = JavaConversions.bufferAsJavaList(scalaBuffer);

System.out.println(javaList == javaListAgain); // true