Scala编程中常见错误：Error:(24, 29) value foreach is not a member of java.util.Set[String]

问题:

在Scala编程开发中, 经常会出现类似如下的错误,

Error:(24, 29) value foreach is not a member of java.util.Set[String]

for (key <- reducedList.keySet) {

^

或

Error:(21, 22) value filter is not a member of java.util.ArrayList[myakka.messages.Word]

for (wc: Word <- dataList) {

^

解决方法:

因为reducedList是java.util.HashMap, 没有foreach方法, 所以需要将其转换为Scala的集合类型,

因此需要在代码中加入如下内容(Scala支持与Java的隐式转换),

import scala.collection.JavaConversions._