CODEWITHSUNDEEP
javajava-8java-stream
maloney
maloney

Reputation: 1663

Java 8 map streams

Is there a way to make this code use Java 8? 

public static boolean areBooleansValid(Map<String, Object> pairs, List<String> errors, String... values) {
    for (String value : values) {
        if (pairs.get(value) == null) {
            return false;
        } else if (!(pairs.get(value) instanceof Boolean)) {
            errors.add(value + " does not contain a valid boolean value");
            return false;
        }
    }
    return true;
}

Was thinking something like this:

Stream<Object> e = Stream.of(values).map(pairs::get);

but how can I get it to return the different boolean values from this stream?

Upvotes: 3

Views: 347

Answers (4)

Holger
Holger

Reputation: 298599

You can reproduce exactly the same behavior as your original code using

public static boolean areBooleansValid(Map<String, Object> pairs,
                                       List<String> errors, String... values) {
    Optional<String> opt = Arrays.stream(values)
        .filter(s -> !(pairs.get(s) instanceof Boolean))
        .findFirst();
    opt .filter(s -> pairs.get(s) != null)
        .ifPresent(value -> errors.add(value+" does not contain a valid boolean value"));
    return !opt.isPresent();
}

Just like your original code, it just searches for the first item that is not a Boolean (might be null), but adds an error only if the value is not null.

Upvotes: 2

curlyBraces
curlyBraces

Reputation: 1105

If you just want to filter out the values that are Boolean and present in the pairs map, you can apply filter function:

Stream.of(values).filter(value ->  pairs.get(value) != null && pairs.get(value) instanceof Boolean)

Or if you want to actually return true and false values, you can use map:

return Stream.of(values).allMatch(value -> {
            if (pairs.get(value) == null) {
                return false;
            }
            if ((pairs.get(value) instanceof Boolean)) {
                return true;
            }
            errors.add(value + " does not contain a valid boolean value");
            return false;
        });

Upvotes: 3

Ilya
Ilya

Reputation: 728

    List<Object> errors = Stream.of(values)
        .filter(value -> value == null || !(pairs.get(value) instanceof Boolean))
        .collect(Collectors.toList());
    List<String> errorMsg = errors.stream().filter(Objects::nonNull)
        .map(value -> "" + pairs.get(value) + " does not contain a valid boolean value")
        .collect(Collectors.toList());
    errors.addAll(errorMsg);
return errors.isEmpty();

Upvotes: 0

Youcef LAIDANI
Youcef LAIDANI

Reputation: 60046

I think you need Just :

return Arrays.stream(values)
       .allMatch(value -> pairs.get(value) instanceof Boolean);

Notes

  • I don't see any reason of error in your method
  • also as @Andy Turner mention in comment pairs.get(value) instanceof Boolean implies pairs.get(value) != null so you don't need to use pairs.get(value) != null

Upvotes: 3

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