如何将嵌套的复杂 scala Map 转换为 Java

Question

我正在尝试在我的 Java 程序中使用 Scala 库，但在将复杂的 Scala Map 转换为 Java 时遇到了一些困难。

我使用的 Scala 对象方法具有以下返回类型：scala.collection.mutable.Map<String, Map<Object, Seq<Object>>>

如何将其转换为 Java 等效的 Map<String, Map<Object, List<Object>>> ？

我已经玩过 JavaConversions 和 JavaConvertors 包，但没有运气:(

public void getPartitionAssignmentForTopics(final List<String> topics) {
    final Seq<String> seqTopics =         scala.collection.JavaConversions.asScalaBuffer(topics).toList();
    scala.collection.mutable.Map<String, Map<Object, Seq<Object>>> map2 = zkUtils
            .getPartitionAssignmentForTopics(seqTopics);

    val map:scala.collection.mutable.Map[String, Map[Object, Seq[Object]]] = scala.collection.mutable.Map()
    map:
    collection.mutable.Map[String, Map[Object, Seq[Object]]] =Map()
    map.mapValues(_.mapValues(_.asJava).asJava).asJava
    res2:
    java.util.Map[String, java.util.Map[Object, java.util.List[Object]]] ={}
}

这不会编译:)

我的意思是我使用以下代码将 Scala Seq 转换为 Java List： scala.collection.JavaConversions.seqAsJavaList(zkUtils.getAllTopics());

Answer 1

我最终得到了以下代码。不是很好：D

public java.util.Map<String, java.util.Map<Integer, java.util.List<Integer>>> getPartitionAssignmentForTopics(final List<String> topics) {
    final scala.collection.Seq<String> seqTopics = scala.collection.JavaConversions.asScalaBuffer(topics).toList();
    scala.collection.mutable.Map<String, scala.collection.Map<Object, scala.collection.Seq<Object>>> tmpMap1 =
            zkUtils.getPartitionAssignmentForTopics(seqTopics);

    final java.util.Map<String, java.util.Map<Integer, java.util.List<Integer>>> result = new HashMap<>();
    java.util.Map<String, Map<Object, Seq<Object>>> tmpMap2 = JavaConversions.mapAsJavaMap(tmpMap1);
    tmpMap2.forEach((k1, v1) -> {
        String topic = (String)k1;
        java.util.Map<Object, Seq<Object>> objectSeqMap = JavaConversions.mapAsJavaMap(v1);
        java.util.Map<Integer, List<Integer>> tmpResultMap = new HashMap<>();
        objectSeqMap.forEach((k2, v2) -> {
            Integer tmpInt = (Integer)k2;
            List<Integer> tmpList = (List<Integer>)(Object)JavaConversions.seqAsJavaList(v2);
            tmpResultMap.put(tmpInt, tmpList);
        });
        result.put(topic, tmpResultMap);
    });

    return result;
}