java - CompletableFuture 立即失败

Question

<分区>

Answer 1

我在 Java 8 的标准库中找不到一个失败的 future 的工厂方法(Java 9 修复了这个问题，正如 Sotirios Delimanolis 所指出的)，但是创建一个很容易:

/**
 * Creates a {@link CompletableFuture} that has already completed
 * exceptionally with the given {@code error}.
 *
 * @param error the returned {@link CompletableFuture} should immediately
 *              complete with this {@link Throwable}
 * @param <R>   the type of value inside the {@link CompletableFuture}
 * @return a {@link CompletableFuture} that has already completed with the
 * given {@code error}
 */
public static <R> CompletableFuture<R> failed(Throwable error) {
    CompletableFuture<R> future = new CompletableFuture<>();
    future.completeExceptionally(error);
    return future;
}