Filter on a value of inner Map using Java 8 streams

adbdkb :

I have a map of maps - Map> - collection.

I need to filter the map and get the outer map that has a given value for a given key of the inner map.

I tried some combinations, but it is not working.

How do I achieve this.

This is what I have tried

Map<String, Map<String, String>> originalMap = getOriginalMap();

String channelId = "channelIdVal";

Map<String, Map<String, String>> filteredMapForKey = originalMap.entrySet().stream()
    .collect(Collectors.toMap(Map.Entry::getKey,
        e -> e.getValue().entrySet().stream().filter(innerMap -> innerMap.getValue().equalsIgnoreCase(channelId)).collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue))));

Basically, I am expecting the filteredMapForKey to have a single entry whose inner map ( the value of the entry ) to contain a key whose value is channelId

How do I achieve that. The above code is returning the entire original map with same keys but empty inner maps except for the valid one. For the valid map, instead of returning the complete inner map, it is only return the map with the key and value of matching channel id

Thanks

Naman :

Seems like there are two things to correct here:

1. The filter logic to filter in entries instead of filtering them out.

2. To filter only those outer entries for which inner map satisfies the condition stated.

You can achieve that as:

Map<String, Map<String, String>> filteredMapForKey = originalMap.entrySet()
        .stream()
        .filter(e -> e.getValue()
                .values()
                .stream()
                .anyMatch(innerMapVal -> innerMapVal.equalsIgnoreCase(channelId)))
        .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

This filters all the outer map entries such that, the inner map for them has a value that is equal(ignoreCase) to the given channelId and then collects these entries into a similar Map as the input.