java 8 streams copy specific objects from map to list

Question

Looking for alternative code in Java8/streams.
I want to copy specific values from a Map into a List using a predefined array of Keys.

The code to accomplish this task in Java 7 is as follows:

public List<Fruit> getFruitList(Map<String, Fruit> fruitMap) {
    final String[] fruitNames = { "apple", "banana", "mango" };
    final ArrayList<Fruit> fruitList = new ArrayList<>(fruitNames.length);
    for (int i = 0; i < fruitNames.length; i++) {
        final String fruitName = fruitNames[i];
        final Fruit fruit = fruitMap.get(fruitName);
        if (fruit != null) {
            fruitList.add(fruit);
        }
    }
    fruitList.trimToSize();
    return fruitList;
}

Pankaj Singhal · Accepted Answer · 2020-10-06 17:02:50Z

2

Figured out a possible solution myself:

return Stream.of(fruitNames)
             .map(fruitMap::get)
             .filter(Objects::nonNull)
             .collect(Collectors.toList());

edited Oct 6, 2020 at 17:02

Pankaj Singhal

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answered Oct 6, 2020 at 16:38

ViV

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1 Comment

Pankaj Singhal Over a year ago

Might wanna use Objects.nonNull. A good alternative to have clean lambda code.

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