CODEWITHSUNDEEP
javajava-8java-stream
methuselah
methuselah

Reputation: 13216

Filter list of maps by value and return map

If I have a List<Map<String, String>> object such as this currencyList :

0
   0 = "product_id" -> 145
   1 = "currency" -> USD
1
   0 = "product_id" -> 105
   1 = "currency" -> EUR
2
   0 = "product_id" -> 102
   1 = "currency" -> EUR

How do I then filter where currency=EUR?

Something like...

List<Map<String, String>> eurCurrencyList 
             = currencyList.stream()
                           .anyMatch(map -> map.containsValue("EUR"));

but that doesn't return a boolean but returns a map like this:

0
   0 = "product_id" -> 105
   1 = "currency" -> EUR
1
   0 = "product_id" -> 102
   1 = "currency" -> EUR

Upvotes: 1

Views: 4067

Answers (2)

Thiyagu
Thiyagu

Reputation: 17920

You need to use filter to filter and can collect to list using Collectors.toList().

List<Map<String, String>> eurCurrencyList = currencyList.stream()
        .filter(map -> map.containsValue("EUR"))
        .collect(Collectors.toList());

EDIT:

If the map can have many entries, it may be inefficient to use containsValue. Instead you can do .filter(map -> map.containsKey(key) && map.get(key).equals(value)) as mentioned in YCF_L@'s answer.

Upvotes: 4

Youcef LAIDANI
Youcef LAIDANI

Reputation: 60045

How do I then filter where currency=EUR?

You have to use filter like so :

String key = "currency", value = "EUR";
List<Map<String, String>> eurCurrencyList = currencyList.stream()
        .filter(map -> map.containsKey(key) && map.get(key).equals(value))
        .collect(Collectors.toList());

Note, Instead of :

map.containsValue("EUR")

You have to use :

.filter(map -> map.containsKey(key) && map.get(key).equals(value))

You have to check if the map contain that key and the value.

Upvotes: 4

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