CODEWITHSUNDEEP
javalambdajava-8java-streamcollectors
jawsh
jawsh

Reputation: 173

Java Stream - Combine filter and collect

ColumnFamily column = tokens.getColumnFamilies().stream()
    .filter(family -> family.getName().equals("this_family"))
    .findAny()
    .get();

Map<String, String> tokenized = column.getColumns().stream()
    .collect(Collectors.toMap(
        Column::getQualifier,
        Column::getValue
    ));

Is there a way I can combine these two streams into one? I am using the first stream to filter and find on my nested list, and using the second stream to create a map based on the result of the stream. I am wondering if there's a way I could have done this using a single stream.

Something like this

Map<String, String> tokenized = tokens.getColumnFamilies().stream()
    .filter(family -> family.getName().equals("this_family"))
    .collect(Collectors.toMap(
        //
    ));

Upvotes: 1

Views: 679

Answers (2)

Eklavya
Eklavya

Reputation: 18430

Use Optional#map() and combine

Map<String, String> tokenized = tokens.getColumnFamilies().stream()
                    .filter(family -> family.getName().equals("this_family"))
                    .findAny()
                    .map(cf -> cf.getColumns().stream()).get()
                    .collect(Collectors.toMap(Column::getQualifier, Column::getValue));

Upvotes: 0

Andronicus
Andronicus

Reputation: 26046

You can use flatMap to get nested Stream and flatten the structure:

Map<String, String> tokenized = tokens.getColumnFamilies().stream()
    .filter(family -> family.getName().equals("this_family"))
    .limit(1)  // equivalent of findAny
    .flatMap(cf -> cf.getColumns().stream())
    .collect(Collectors.toMap(
        Column::getQualifier,
        Column::getValue
    ));

Upvotes: 2

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