我有一個異步函數調用其他異步函數。在Java中，如何等到異步調用完成（包括其中的任何嵌套異步調用）。我已經可以調用未來了，但沒有運氣。示例代碼：void asyncMehodA(){ }void asyncMethodB() {asyncMehodA();}我嘗試了未來可調用的方式：final Callable<Void> callable1 = new Callable<Void>() { @Override public Void call() { asyncMethodB(); return null; } };final Future<Void> callableFuture = mExecutor.submit(callable1); try { callableFuture.get(); } catch (final InterruptedException | ExecutionException e) {}希望 get 函數將阻塞執行，直到異步返回。但似乎 get 函數將觸發異步調用并恢復 null。而不是等待異步完成其執行。我在驗證了日志語句中添加了相同的日志語句。如果我的理解是錯誤的，請糾正我。建議任何其他可以幫助我的概念。
2 回答
qq_笑_17
TA貢獻1818條經驗 獲得超7個贊
下面是一個使用倒計時批處理的示例。
package chapter13;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class BST {
public static void main(String[] args) throws InterruptedException {
final CountDownLatch latch = new CountDownLatch(1);
final ExecutorService executorService = Executors.newCachedThreadPool();
Runnable runnableA = () -> {
System.out.println("Runnable A");
latch.countDown();
System.out.println("Runnable A finished");
};
Runnable runnableB = () -> {
System.out.println("Runnable B");
executorService.submit(runnableA);
try {
System.out.println("Runnable B waiting for A to complete");
latch.await();
System.out.println("Runnable B finished");
} catch (InterruptedException e) {
System.out.println("Thread interrupted");
Thread.currentThread().interrupt();
}
};
executorService.submit(runnableB);
Thread.sleep(10);
shutDown(executorService);
}
private static void shutDown(ExecutorService executorService) {
executorService.shutdown();
try {
if (!executorService.awaitTermination(1, TimeUnit.SECONDS)) {
executorService.shutdownNow();
}
} catch (InterruptedException e) {
executorService.shutdownNow();
}
}
}
我使用方法使主線程休眠，因為在提交任務 B 后立即關閉池可能會導致池在任務 B 提交任務 A 之前停止接受新任務。Thread.sleep()
DIEA
TA貢獻1820條經驗 獲得超2個贊
一種方法是使用java鎖定方法。例如：
private AtomicBoolean processed = new AtomicBoolean(true) ;
private String result = null ;
public String doAndWait()
{
synchronized(processed) {
doSomethingAsync() ;
processed.wait();
}
return result ;
}
public void doSomethingAsync()
{
...
result="OK";
synchronized(processed) {
processed.notify();
}
}
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