6 
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

class Task implements Callable<String> {
    public String call() throws Exception {
        String s = "initial";
        try {
            System.out.println("Started..");
            /*for (int i=0;i<10000;i++) {
                if (i % 2 == 0) {
                    System.out.println("Even");
                }
            }*/
            boolean flag = true;
            while(flag) {

            }
            System.out.println("Finished!");
            s = "Done";
        }
        catch (RuntimeException e) {
            s = "RuntimeException";
        }
        catch (Exception e) {
            s = "Exception";
        }
        finally {

        }
        return s;
    }
}

public class ExecutorServiceTest {

    public static void main(String[] args) throws Exception {
        ExecutorService executor = Executors.newSingleThreadExecutor();
        List<Future<String>> result = executor.invokeAll(Arrays.asList(new Task()), 5, TimeUnit.SECONDS);
        executor.shutdown();
        Iterator<Future<String>> iter = result.iterator();
        while (iter.hasNext()) {
            System.out.println("Came here");
            Future<String> fut = iter.next();
            System.out.println(fut.get());
        }
    }
}

有没有办法让我停止执行无限循环的线程？

4

2 回答 2

7

是的，您可以将flag（或逻辑上&&）替换为!Thread.currentThread().isInterrupted().

这样，当任务被取消时，循环就会终止。

循环看起来像这样：

while(!Thread.currentThread().isInterrupted() && flag) {
  /* Do work. */
}

使用应该是这样的：

ExecutorService executor = Executors.newSingleThreadExecutor();
Future<String> task = executor.submit(new Task());
String str;
try {
  str = task.get(5, TimeUnit.SECONDS);
} finally {
  task.cancel(true);
}
于 2010-03-01T18:44:59.240 回答
0

考虑使用synchronized (this) { this.wait() }而不是sleepinside call()，然后当您在flag外部设置布尔值时（可能直接或通过flag()方法；通过直接访问确保您的标志变量是volatile）调用task.notifyAll()以唤醒睡眠线程（确保您的任务对象是局部变量而不是让它匿名，以便您可以在其上调用方法，并在Task) 中将标志标记为类属性。

这样也会更有效率，因为循环会不必要地浪费循环——确切的机制称为“保护块”（http://java.sun.com/docs/books/tutorial/essential/concurrency/guardmeth.html）。当您从等待中醒来时，测试标志变量以确保它已设置。

编辑：更仔细地查看了原始问题，并使用现有代码和原则创建了一个示例（给猫剥皮的方法不止一种 :)）。试试这个——这里的循环由于当前线程的中断状态而退出，由于超时而被取消：

package ett;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

class Task implements Callable<String> {
    public String call() throws Exception {
        String s = "initial";
        System.out.println("Started..");
        for (int i=0;;i++) {
            if (i % 2 == 0) {
                System.out.println("Even");
            }
            Thread.yield();
            if (Thread.interrupted()) break;
        }
        System.out.println("Finished!");
        s = "Done";

        return s;
    }
}

public class ExecutorServiceTest {

    public static void main(String[] args) throws Exception {
        ExecutorService executor = Executors.newSingleThreadExecutor();
        List<Future<String>> result = executor.invokeAll(Arrays.asList(new Task()), 1, TimeUnit.SECONDS);
        executor.shutdown();

        System.out.println("came here");

        for (Future<String> f : result) {
            try {
                System.out.println(f.get());
            } catch (CancellationException e) {
                e.printStackTrace();
            }
        }
    }
}
于 2010-03-01T18:53:40.023 回答