CompletableFutureUtil.java

import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.Future;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * @author cqy
 * @since 2017/7/29.
 */
public abstract class CompletableFutureUtil {

    public static <T> CompletableFuture<List<T>> sequence(List<CompletableFuture<T>> futures) {
        CompletableFuture<Void> allDoneFuture = CompletableFuture.allOf(futures.toArray(new CompletableFuture[futures.size()]));
        return allDoneFuture.thenApply(v -> futures.stream().map(CompletableFuture::join).collect(Collectors.<T>toList()));
    }

    public static <T> CompletableFuture<Stream<T>> sequence(Stream<CompletableFuture<T>> futures) {
        CompletableFuture<Void> allDoneFuture = CompletableFuture.allOf(futures.toArray(CompletableFuture[]::new));
        return allDoneFuture.thenApply(v -> futures.map(CompletableFuture::join));
    }

    public static <T> CompletableFuture<T> toCompletable(Future<T> future, Executor executor) {
        if (future instanceof CompletableFuture) {
            return (CompletableFuture<T>) future;
        }
        return CompletableFuture.supplyAsync(() -> {
            try {
                return future.get();
            } catch (InterruptedException | ExecutionException e) {
                throw new RuntimeException(e);
            }
        }, executor);
    }
}