How to return value by ternary condition in a stream?

Question

I want to return a value of a stream based on a condition. Take the following as an example only, where I want to map any apple to Food.APPLE:

public enum Food {
    APPLE, APPLE2, APPLE3, BANANA, PINEAPPLE, CUCUMBER;

    private static final Food[] APPLES = new Food[] {APPLE, APPLE2, APPLE3};

    //java7
    public Food fromValue(String value) {
        for (Food type : Food.values()) {
            if (type.name().equalsIgnoreCase(value)) {
                return ArrayUtils.contains(APPLES, type) ? APPLE : type;
            }
        }
        return null;
    }

    //java8: how to include the array check for APPLES?
    public Food fromValue(String value) {
        return Arrays.stream(Food.values()).
            filter(type -> type.name().equalsIgnoreCase(value))
            .findFirst()
            .orElse(null);
    }
}

How can I include the ternary condition in a stream?

Answer 1

You could do it like this:

import static java.util.AbstractMap.SimpleImmutableEntry;

...

enum Food {
    APPLE, APPLE2, APPLE3, BANANA, PINEAPPLE, CUCUMBER;

    private static final Map<String, Food> MAP = Stream.concat(
                Stream.of(APPLE, APPLE2, APPLE3).map(e -> new SimpleImmutableEntry<>(e.name().toLowerCase(), APPLE)),
                Stream.of(BANANA, PINEAPPLE, CUCUMBER).map(e -> new SimpleImmutableEntry<>(e.name().toLowerCase(), e)))
            .collect(toMap(SimpleImmutableEntry::getKey, SimpleImmutableEntry::getValue));

    public static Food fromValue(String value) {
        return MAP.get(value.toLowerCase());
    }
}

The lookup in the map will be O(1).