Convert Map<String, List<Object>> to Map<String, List<String>> in java 1.8

Question

I have a Map<String, List<Object>> , I would like to convert it to Map<String, List<String>> in java 8 .

In Java 1.7 I was using a function to extract value from Map and then wrote another method declared empty List , used for loop to extract each element and then added to List Object in java 1.7

Any suggestions to do same in java 8 using lambda expressions

Thanks in advance

What are these objects? How do you intend to convert them to strings? — shmosel
– shmosel, Commented Apr 4, 2019 at 4:31

Kartik · Accepted Answer · 2019-04-04 03:07:34Z

1

You can use this:

Map<String, List<String>> result = map.entrySet().stream()
        .map(e -> Map.entry(e.getKey(),
                e.getValue().stream()
                        .map(o -> (String) o) //or Object::toString depending on the object
                        .collect(Collectors.toList())))
        .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

Map.entry is from Java 9, you can use AbstractMap.SimpleEntry if you are on Java 8.

edited Apr 4, 2019 at 3:07

answered Apr 4, 2019 at 2:59

Kartik

7,9456 gold badges33 silver badges55 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Convert Map<String, List<Object>> to Map<String, List<String>> in java 1.8

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related