PoC List of Try

PocTry.java

package fp;

import io.vavr.control.Try;

import java.util.List;
import java.util.Random;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class PocTry {

    private static Random random = new Random();

    private static String buildString(int i) {
        if (random.nextBoolean()) {
            return String.valueOf(i);
        } else {
            throw new RuntimeException("error for " + i);
        }
    }

    private static List<String> build() {
        return IntStream.range(0, 20)
                .mapToObj(i -> Try.of(() -> buildString(i)))
                .flatMap(t -> {
                    if (t.isFailure()) {
                        System.out.println(t.getCause().getMessage());
                        return Stream.empty();
                    } else {
                        return Stream.of(t.get());
                    }
                }).collect(Collectors.toList());
    }

    public static void main(String... args) {
        build().forEach(System.out::println);
    }

}

Example using http://vavr.io

import io.vavr.collection.Iterator; // could be also any other collection, including List, Vector, Stream, Queue, ...
import io.vavr.control.Try;
import static io.vavr.API.*; // for println shortcut

Iterator.range(0, 20)
    .map(i -> Try.of(() -> buildString(i)))
    .flatMap(t -> t.onFailure(x -> println(x.getMessage())))
    .toJavaList();

Explanation:

• flatMap operates on Iterable instances. So collection can flatMap elements of type Try, Option, all java/vavr collections etc.
• toJavaList returns a java.util.List instance in O(n)
• if the collection is a Seq (like List, Vector, Stream, Array, ...), there are methods asJava() and asJavaMutable(), which return immutable/mutable views of type java.util.List in O(1)

Thanks !