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I am using Spark. In spark after doing a collect on RDDs of scala.Tuple2<K,V> I get List of scala.Tuple2<K,V> . I want to convert it to a HashMap<K,V> in Java.

I can iterate over the list and add it to my HashMap but I am looking for an elegant way to do this. Thanks!

scala> import scala.collection.JavaConverters._
scala> val tuples = List((1, 2), (2, 3), (4, 5))
scala> tuples.toMap.asJava
res1: java.util.Map[Int,Int] = {1=2, 2=3, 4=5}
I think the most elegant way in java is to use stream and Collectors.
You can achieve this way:
    List<Tuple2<String, String>> list = new ArrayList<>();
    list.add(new Tuple2<>("first", "second"));
    list.add(new Tuple2<>("third", "four"));
    list.add(new Tuple2<>("five", "six"));
    list.add(new Tuple2<>("seven", "eight"));
    list.add(new Tuple2<>("nine", "ten"));
    System.out.println("List of Tuple2s:" + list); 
    //convert list of tupples to Map with one line
    Map<String, String> resultMap = list.stream()
            .collect(Collectors.toMap(Tuple2::_1, Tuple2::_2));
    System.out.println("Map of Tuples2s: "+resultMap);
Output:
    List of Tuple2s:[(first,second), (third,four), (five,six), (seven,eight), (nine,ten)]
    Map of Tuples2s: {nine=ten, third=four, seven=eight, five=six, first=second}
But what about duplicate keys?? When we add another item to list like: list.add(new Tuple2<>("first", "ten")); exception occures:
  
Exception in thread "main" java.lang.IllegalStateException: Duplicate
  key second    at
  java.util.stream.Collectors.lambda$throwingMerger$0(Collectors.java:133)
    at java.util.HashMap.merge(HashMap.java:1253)
If you are not sure whether you can have duplicates you can do:
    Map<String, String> resultMap = list.stream()
            .collect(Collectors.toMap(Tuple2::_1, Tuple2::_2,
                    (x, y) -> {
                        System.out.println("duplicate key!");
                        return x;
and avoid overwriting item in Map.
Output:
List of Tuple2s:[(first,second), (third,four), (five,six), (seven,eight), (nine,ten), (first,ten)]
duplicate key!
Map of Tuples2s: {nine=ten, third=four, seven=eight, five=six, first=second}
        
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