Java do stuff_超时与Java 8中的默认值CompletableFuture

CompletableFuture.supplyAsync只是一个帮助方法，为您创建一个CompletableFuture，并将任务提交到ForkJoin池。

您可以根据您的要求创建自己的supplyAsync：

private static final ScheduledExecutorService schedulerExecutor =

Executors.newScheduledThreadPool(10);

private static final ExecutorService executorService =

Executors.newCachedThreadPool();

public static CompletableFuture supplyAsync(

final Supplier supplier, long timeoutValue, TimeUnit timeUnit,

T defaultValue) {

final CompletableFuture cf = new CompletableFuture();

// as pointed out by Peti, the ForkJoinPool.commonPool() delivers a

// ForkJoinTask implementation of Future, that doesn't interrupt when cancelling

// Using Executors.newCachedThreadPool instead in the example

// submit task

Future> future = executorService.submit(() -> {

try {

cf.complete(supplier.get());

} catch (Throwable ex) {

cf.completeExceptionally(ex);

}

});

//schedule watcher

schedulerExecutor.schedule(() -> {

if (!cf.isDone()) {

cf.complete(defaultValue);

future.cancel(true);

}

}, timeoutValue, timeUnit);

return cf;

}

使用该帮助器创建CompletableFuture与在CompletableFuture中使用静态方法一样简单：

CompletableFuture a = supplyAsync(() -> "hi", 1,

TimeUnit.SECONDS, "default");

测试：

a = supplyAsync(() -> {

try {

Thread.sleep(2000);

} catch (InterruptedException e1) {

// ignore

}

return "hi";

}, 1, TimeUnit.SECONDS, "default");