CODEWITHSUNDEEP
scalafunctional-programmingmapsconcatenation
Binara Medawatta
Binara Medawatta

Reputation: 532

Removing duplicate keys when concatenating maps in SCALA

While I was studying for my exams I encountered this question. Searched on google but couldn't find an answer.

When we concatenate two maps using either the ++ operator or the Map.++() method duplicate keys will get removed. But what will happen if there are duplicate keys but different values for the keys in two maps, which one will be removed?

ex:

Map1 contains key1->"hello"

Map2 contains key1->"world"

Here keys have the same name but the values are different so what will be the key-value pairs in the output map when Map1 and Map2 are concatenated?

Upvotes: 1

Views: 1202

Answers (1)

Sergey Romanovsky
Sergey Romanovsky

Reputation: 4554

If you'd like to be explicit in overriding/merging logic you can do something like:

val map1 = Map("key1" -> "hello")
val map2 = Map("key1" -> "world")

val jointKeys = map1.keySet.intersect(map2.keySet)
val overlap = jointKeys.map(key => (key -> map2(key))).toMap // or use whatever custom override/concatenate logic instead of this lambda
val merged = overlap ++ map1.filterKeys(jointKeys) ++ map2.filterKeys(jointKeys)

Upvotes: 3

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