Java 如何使用ExecutorService等待所有线程完成？
我需要一次执行4个任务，如下所示：Java 如何使用ExecutorService等待所有线程完成？,java,multithreading,concurrency,parallel-processing,executorservice,Java,Multithreading,Concurrency,Parallel Processing,Executorservice,我需要一次执行4个任务，如下所示： ExecutorService taskExecutor = Executors.newFixedThreadPool(4); while(...) { taskExecutor.execute(new MyTask()); } //...wait for completion somehow 一旦全部完成，如何通知我？现在我想不出比设置一些全局任务计数器更好的方法了，在每个任务结束时减少它，然后在无限循环中监视这个计数器变成0；或者获取一个未来列表
ExecutorService taskExecutor = Executors.newFixedThreadPool(4);
while(...) {
taskExecutor.execute(new MyTask());
}
//...wait for completion somehow
您可以将任务包装在另一个runnable中，它将发送通知：
taskExecutor.execute(new Runnable() {
public void run() {
taskStartedNotification();
new MyTask().run();
taskFinishedNotification();
}
});
您可以使用自己的子类包装
taskExecutorExecutorService taskExecutor = Executors.newFixedThreadPool(4);
List<Callable<?>> tasks; // your tasks
// invokeAll() returns when all tasks are complete
List<Future<?>> futures = taskExecutor.invokeAll(tasks);
ExecutorService taskExecutor=Executors.newFixedThreadPool（4）；
List>futures=taskExecutor.invokeAll（任务）；
CountDownLatch信号量来完成
ExecutorService taskExecutor = Executors.newFixedThreadPool(4);
int numberOfTasks=0;
Semaphore s=new Semaphore(0);
while(...) {
taskExecutor.execute(new MyTask());
numberOfTasks++;
}
try {
s.aquire(numberOfTasks);
...
在您的任务中，只需调用s.release（）
，就像调用lack.countDown（）一样您还可以使用期货列表：
List<Future> futures = new ArrayList<Future>();
// now add to it:
futures.add(executorInstance.submit(new Callable<Void>() {
public Void call() throws IOException {
// do something
return null;
}
}));
基本上，诀窍是每次对未来的每个对象调用.get（），而不是无限循环调用（all或each）上的isDone（）。因此，您可以保证在最后一个线程结束时“继续前进”并通过此块。需要注意的是，由于.get（）调用重新引发异常，如果其中一个线程死亡，您可能会在其他线程完成之前引发异常[为了避免这种情况，您可以在get调用周围添加一个catch ExecutionException
]。另一个警告是，它保留了对所有线程的引用，因此，如果它们有线程局部变量，则在您通过此块之前，它们不会被收集（尽管如果出现问题，您可以通过从ArrayList中删除Future来解决此问题）。如果你想知道哪一个将来“先完成”，你可以使用一些类似的东西，比如我刚刚编写了一个示例程序来解决你的问题。没有给出简明的实现，所以我将添加一个。虽然可以使用executor.shutdown（）
和executor.waittermination（）
，但这不是最佳做法，因为不同线程所用的时间是不可预测的
ExecutorService es = Executors.newCachedThreadPool();
List<Callable<Integer>> tasks = new ArrayList<>();
for (int j = 1; j <= 10; j++) {
tasks.add(new Callable<Integer>() {
@Override
public Integer call() throws Exception {
int sum = 0;
System.out.println("Starting Thread "
+ Thread.currentThread().getId());
for (int i = 0; i < 1000000; i++) {
sum += i;
}
System.out.println("Stopping Thread "
+ Thread.currentThread().getId());
return sum;
}
});
}
try {
List<Future<Integer>> futures = es.invokeAll(tasks);
int flag = 0;
for (Future<Integer> f : futures) {
Integer res = f.get();
System.out.println("Sum: " + res);
if (!f.isDone())
flag = 1;
}
if (flag == 0)
System.out.println("SUCCESS");
else
System.out.println("FAILED");
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
Executors服务=Executors.newCachedThreadPool（）；
列表任务=新建ArrayList（）；
对于（int j=1；j在executorgetActiveCount（）
中有一个方法，它给出活动线程的计数
在跨越线程之后，我们可以检查activeCount（）
值是否为0
。一旦该值为零，则表示当前没有正在运行的活动线程，这意味着任务已完成：
while (true) {
if (executor.getActiveCount() == 0) {
//ur own piece of code
break;
}
}
比赛有点晚了，但为了完成比赛
不要“等待”所有任务完成，你可以用好莱坞的原则来思考，“不要打电话给我，我会打电话给你”——当我完成时。
我认为生成的代码更优雅
番石榴提供了一些有趣的工具来实现这一点
例如：
将ExecutorService包装到ListingExecutorService中：
ListeningExecutorService service = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(10));
提交可调用项集合以执行：：
for (Callable<Integer> callable : callables) {
ListenableFuture<Integer> lf = service.submit(callable);
// listenableFutures is a collection
listenableFutures.add(lf)
});
for（Callable Callable:callables）{
ListenableFuture lf=服务提交（可调用）；
//listenableFutures是一个集合
listenableFutures.add（左前）
});
现在是关键部分：
ListenableFuture<List<Integer>> lf = Futures.successfulAsList(listenableFutures);
ListenableFuture lf=Futures.successfulAsList（listenableFutures）；
将回调附加到ListenableFuture，可用于在所有期货完成时收到通知：
Futures.addCallback(lf, new FutureCallback<List<Integer>> () {
@Override
public void onSuccess(List<Integer> result) {
// do something with all the results
}
@Override
public void onFailure(Throwable t) {
// log failure
}
});
Futures.addCallback（lf，newfutureCallback（）{
@凌驾
成功时公开作废（列表结果）{
//用所有的结果做点什么
}
@凌驾
失效时的公共无效（可丢弃的t）{
//日志失败
}
});
这还提供了一个优势，即处理完成后，您可以在一个位置收集所有结果
更多信息这可能会有所帮助
Log.i(LOG_TAG, "shutting down executor...");
executor.shutdown();
while (true) {
try {
Log.i(LOG_TAG, "Waiting for executor to terminate...");
if (executor.isTerminated())
break;
if (executor.awaitTermination(5000, TimeUnit.MILLISECONDS)) {
break;
}
} catch (InterruptedException ignored) {}
}
只是为了提供更多不同于使用闩锁/屏障的替代方案。
您还可以获得部分结果，直到所有结果都使用完毕
从实践中的Java并发性：
“如果您有一批计算要提交给执行者，并且您希望在计算完成后检索其结果
如果可用，您可以保留与每个任务关联的未来，并通过使用
超时为零。这是可能的，但是很乏味。幸运的是，有一个更好的方法：完成服务。”
这里是实现
public class TaskSubmiter {
private final ExecutorService executor;
TaskSubmiter(ExecutorService executor) { this.executor = executor; }
void doSomethingLarge(AnySourceClass source) {
final List<InterestedResult> info = doPartialAsyncProcess(source);
CompletionService<PartialResult> completionService = new ExecutorCompletionService<PartialResult>(executor);
for (final InterestedResult interestedResultItem : info)
completionService.submit(new Callable<PartialResult>() {
public PartialResult call() {
return InterestedResult.doAnOperationToGetPartialResult();
}
});
try {
for (int t = 0, n = info.size(); t < n; t++) {
Future<PartialResult> f = completionService.take();
PartialResult PartialResult = f.get();
processThisSegment(PartialResult);
}
}
catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
catch (ExecutionException e) {
throw somethinghrowable(e.getCause());
}
}
}
公共类任务提交器{
私人最终执行人服务执行人；
TaskSubmiter（ExecutorService executor）{this.executor=executor；}
void doSomethingLarge（AnySourceClass源）{
最终列表信息=doPartialAsyncProcess（来源）；
CompletionService CompletionService=新的执行者CompletionService（执行者）；
对于（最终感兴趣的结果感兴趣的结果M:info）
completionService.submit（新的可调用（）{
公共部分结果调用（）{
返回InterestedResult.doAnOperationToGetPartialResult（）；
}
});
试一试{
for（int t=0，n=info.size（）；tListenableFuture<List<Integer>> lf = Futures.successfulAsList(listenableFutures);
Futures.addCallback(lf, new FutureCallback<List<Integer>> () {
@Override
public void onSuccess(List<Integer> result) {
// do something with all the results
}
@Override
public void onFailure(Throwable t) {
// log failure
}
});
Log.i(LOG_TAG, "shutting down executor...");
executor.shutdown();
while (true) {
try {
Log.i(LOG_TAG, "Waiting for executor to terminate...");
if (executor.isTerminated())
break;
if (executor.awaitTermination(5000, TimeUnit.MILLISECONDS)) {
break;
}
} catch (InterruptedException ignored) {}
}
public class TaskSubmiter {
private final ExecutorService executor;
TaskSubmiter(ExecutorService executor) { this.executor = executor; }
void doSomethingLarge(AnySourceClass source) {
final List<InterestedResult> info = doPartialAsyncProcess(source);
CompletionService<PartialResult> completionService = new ExecutorCompletionService<PartialResult>(executor);
for (final InterestedResult interestedResultItem : info)
completionService.submit(new Callable<PartialResult>() {
public PartialResult call() {
return InterestedResult.doAnOperationToGetPartialResult();
}
});
try {
for (int t = 0, n = info.size(); t < n; t++) {
Future<PartialResult> f = completionService.take();
PartialResult PartialResult = f.get();
processThisSegment(PartialResult);
}
}
catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
catch (ExecutionException e) {
throw somethinghrowable(e.getCause());
}
}
}
Runner runner = Runner.runner(4); // create pool with 4 threads in thread pool
while(...) {
runner.run(new MyTask()); // here you submit your task
}
runner.waitTillDone(); // and this blocks until all tasks are finished (or failed)
runner.shutdown(); // once you done you can shutdown the runner
ExecutorService es = Executors.newFixedThreadPool(4);
List<Runnable> tasks = getTasks();
CompletableFuture<?>[] futures = tasks.stream()
.map(task -> CompletableFuture.runAsync(task, es))
.toArray(CompletableFuture[]::new);
CompletableFuture.allOf(futures).join();
es.shutdown();
public class ScheduledThreadPoolExample {
public static void main(String[] args) throws InterruptedException {
ScheduledExecutorService executorService = Executors.newScheduledThreadPool(5);
executorService.scheduleAtFixedRate(() -> System.out.println("process task."),
0, 1, TimeUnit.SECONDS);
TimeUnit.SECONDS.sleep(10);
executorService.shutdown();
executorService.awaitTermination(1, TimeUnit.DAYS);
}
}
final List<Runnable> tasks = ...; //or any other functional interface
tasks.stream().parallel().forEach(Runnable::run) // Uses default pool
//alternatively to specify parallelism
new ForkJoinPool(15).submit(
() -> tasks.stream().parallel().forEach(Runnable::run)
).get();
public class MyTask implements Runnable {
private CountDownLatch countDownLatch;
public MyTask(CountDownLatch countDownLatch {
this.countDownLatch = countDownLatch;
}
@Override
public void run() {
try {
//Do somethings
//
this.countDownLatch.countDown();//important
} catch (InterruptedException ex) {
Thread.currentThread().interrupt();
}
}
}
CountDownLatch countDownLatch = new CountDownLatch(NUMBER_OF_TASKS);
ExecutorService taskExecutor = Executors.newFixedThreadPool(4);
for (int i = 0; i < NUMBER_OF_TASKS; i++){
taskExecutor.execute(new MyTask(countDownLatch));
}
countDownLatch.await();
System.out.println("Finish tasks");
ExecutorService executor = Executors.newFixedThreadPool(10);
CompletableFuture[] futures = new CompletableFuture[10];
int i = 0;
while (...) {
futures[i++] = CompletableFuture.runAsync(runner, executor);
}
CompletableFuture.allOf(futures).join(); // THis will wait until all future ready.
package frss.main;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class TestHilos {
void procesar() {
ExecutorService es = Executors.newFixedThreadPool(4);
List<Runnable> tasks = getTasks();
CompletableFuture<?>[] futures = tasks.stream().map(task -> CompletableFuture.runAsync(task, es)).toArray(CompletableFuture[]::new);
CompletableFuture.allOf(futures).join();
es.shutdown();
System.out.println("FIN DEL PROCESO DE HILOS");
}
private List<Runnable> getTasks() {
List<Runnable> tasks = new ArrayList<Runnable>();
Hilo01 task1 = new Hilo01();
tasks.add(task1);
Hilo02 task2 = new Hilo02();
tasks.add(task2);
return tasks;
}
private class Hilo01 extends Thread {
@Override
public void run() {
System.out.println("HILO 1");
}
}
private class Hilo02 extends Thread {
@Override
public void run() {
try {
sleep(2000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("HILO 2");
}
}
public static void main(String[] args) {
TestHilos test = new TestHilos();
test.procesar();
}
}
ExecutorService es = Executors.newFixedThreadPool(4);
List<Runnable> tasks = getTasks();
CompletableFuture<?>[] futures = tasks.stream()
.map(task -> CompletableFuture.runAsync(task, es))
.toArray(CompletableFuture[]::new);
CompletableFuture.allOf(futures).join();
es.shutdown();
ExecutorService es = Executors.newFixedThreadPool(4);
List< Future<?>> futures = new ArrayList<>();
for(Runnable task : taskList) {
futures.add(es.submit(task));
}
for(Future<?> future : futures) {
try {
future.get();
}catch(Exception e){
// do logging and nothing else
}
}
es.shutdown();
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/** Testing CountDownLatch and ExecutorService to manage scenario where
* multiple Threads work together to complete tasks from a single
* resource provider, so the processing can be faster. */
public class ThreadCountDown {
private CountDownLatch threadsCountdown = null;
private static Queue<Integer> tasks = new PriorityQueue<>();
public static void main(String[] args) {
// Create a queue with "Tasks"
int numberOfTasks = 2000;
while(numberOfTasks-- > 0) {
tasks.add(numberOfTasks);
}
// Initiate Processing of Tasks
ThreadCountDown main = new ThreadCountDown();
main.process(tasks);
}
/* Receiving the Tasks to process, and creating multiple Threads
* to process in parallel. */
private void process(Queue<Integer> tasks) {
int numberOfThreads = getNumberOfThreadsRequired(tasks.size());
threadsCountdown = new CountDownLatch(numberOfThreads);
ExecutorService threadExecutor = Executors.newFixedThreadPool(numberOfThreads);
//Initialize each Thread
while(numberOfThreads-- > 0) {
System.out.println("Initializing Thread: "+numberOfThreads);
threadExecutor.execute(new MyThread("Thread "+numberOfThreads));
}
try {
//Shutdown the Executor, so it cannot receive more Threads.
threadExecutor.shutdown();
threadsCountdown.await();
System.out.println("ALL THREADS COMPLETED!");
//continue With Some Other Process Here
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
/* Determine the number of Threads to create */
private int getNumberOfThreadsRequired(int size) {
int threshold = 100;
int threads = size / threshold;
if( size > (threads*threshold) ){
threads++;
}
return threads;
}
/* Task Provider. All Threads will get their task from here */
private synchronized static Integer getTask(){
return tasks.poll();
}
/* The Threads will get Tasks and process them, while still available.
* When no more tasks available, the thread will complete and reduce the threadsCountdown */
private class MyThread implements Runnable {
private String threadName;
protected MyThread(String threadName) {
super();
this.threadName = threadName;
}
@Override
public void run() {
Integer task;
try{
//Check in the Task pool if anything pending to process
while( (task = getTask()) != null ){
processTask(task);
}
}catch (Exception ex){
ex.printStackTrace();
}finally {
/*Reduce count when no more tasks to process. Eventually all
Threads will end-up here, reducing the count to 0, allowing
the flow to continue after threadsCountdown.await(); */
threadsCountdown.countDown();
}
}
private void processTask(Integer task){
try{
System.out.println(this.threadName+" is Working on Task: "+ task);
}catch (Exception ex){
ex.printStackTrace();
}
}
}
}
ExecutorService executer1 = Executors.newFixedThreadPool(THREAD_SIZE1);
for (<loop>) {
executer1.execute(new Runnable() {
@Override
public void run() {
...
}
});
}
executer1.shutdown();
try{
executer1.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
ExecutorService executer2 = Executors.newFixedThreadPool(THREAD_SIZE2);
for (true) {
executer2.execute(new Runnable() {
@Override
public void run() {
...
}
});
}
executer2.shutdown();
} catch (Exception e){
...
}
List<Future<Void>> results = null;
try {
List<Callable<Void>> tasks = new ArrayList<>();
ExecutorService executorService = Executors.newFixedThreadPool(4);
results = executorService.invokeAll(tasks);
} catch (InterruptedException ex) {
...
} catch (Exception ex) {
...
}