我是 Java 新手。我正在嘗試優化以下方法：public void myLongRunningMethod(){LongRunningOperation1();LongRunningOperation2();LongRunningOperation3();Log.Info("completion message goes here.")}LongRunningOperation1()、LongRunningOperation2() 和 LongRunningOperation3() 相互獨立，它們的完成順序無關緊要。但是只有在所有這些方法調用成功完成后才應該打印日志語句。如果我采用以下方法，由于它使用新線程，我相信方法的完成順序不會得到保證。public String myMethod(){Thread thread1 = new Thread(() -> { LongRunningOperation1();}).start();Thread thread2 = new Thread(() -> { LongRunningOperation2();}).start();Thread thread3 = new Thread(() -> { LongRunningOperation3();}).start();Log.Info("completion message goes here.")}
2 回答
海綿寶寶撒
TA貢獻1809條經驗 獲得超8個贊
正如評論所提到的，最簡單的方法是在 3 個線程中的每一個上調用 join() ：thread1.join(); thread2.join(); thread3.join();
或者使用 aCountDownLatch雖然它涉及更多（但在概念上可能更“正確”）：
latch = new CountDownLatch(3)在完成任務
latch.countDown()后讓每個線程去做。讓主線程
latch.await()- 瞧。
慕工程0101907
TA貢獻1887條經驗 獲得超5個贊
與其手動創建Threads ，不如使用ExecutorService API. 使用ExecutorService您可以提交長時間運行的操作，結果您將收到Future實例，讓您等到操作完成。
請參閱下面的示例，該示例顯示了該想法：
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
public class Threads {
public static void main(String[] args) {
new Threads().myMethod();
}
private String myMethod() {
ExecutorService executor = Executors.newFixedThreadPool(3);
List<Future<?>> futures = new ArrayList<>(3);
futures.add(executor.submit(this::LongRunningOperation1));
futures.add(executor.submit(this::LongRunningOperation2));
futures.add(executor.submit(this::LongRunningOperation3));
for (Future<?> future : futures) {
try {
future.get();
} catch (Exception e) {
e.printStackTrace();
}
}
System.out.println("All operations are finished!");
return "Done";
}
private void LongRunningOperation1() {
sleep(TimeUnit.SECONDS.toMillis(1));
System.out.println("LongRunningOperation1 is finished!");
}
private void LongRunningOperation2() {
sleep(TimeUnit.SECONDS.toMillis(2));
System.out.println("LongRunningOperation2 is finished!");
}
private void LongRunningOperation3() {
sleep(TimeUnit.SECONDS.toMillis(3));
System.out.println("LongRunningOperation3 is finished!");
}
private void sleep(long millis) {
try {
Thread.sleep(millis);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
上面的代碼打?。?/p>
LongRunningOperation1 is finished!
LongRunningOperation2 is finished!
LongRunningOperation3 is finished!
All operations are finished!
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