ExecutorService 和写入文件 [重复]

Question

我正在尝试使用ExecutorService 来写入文件。但是，当我执行这段代码时，在执行完成之前执行到outFile.close();，这会抛出

java.io.IOException: Stream closed

如何才能在所有任务完成后才能拨打outFile.close()？

（PS：为了代码清晰，我已经删除了所有的 try/catch 块。）

ExecutorService executor = Executors.newFixedThreadPool(3);

for (int i = 1; i <= 1000; i++) {
  final int counter = i;
  executor.execute(new Runnable() {
    @Override
    public void run() {
      outFile.write(wld.getWord(counter) + "successful");
      outFile.write("\n");
    }               
  });
}

outFile.close();

Answer 1

您应该首先等待所有任务完成。提交所有作业后，您可以调用executor.shutdown() 并等待所有线程使用executor.awaitTermination() 完成。

这是一个例子：

ExecutorService executor = Executors.newFixedThreadPool(3);

for (int i = 1; i <= 1000; i++) {
      final int counter = i;
      executor.execute(new Runnable() {
          @Override
          public void run() {
              outFile.write(wld.getWord(counter) + "successful");
              outFile.write("\n");
          }               
      });
}

executor.shutdown(); //shut down executor
executor.awaitTermination(60, TimeUnit.SECONDS); //waiting for 60 seconds

outFile.close(); //and then you may safely close the stream knowing that all the tasks have finished

注意：由于超时，主线程可能会在所有作业完成之前唤醒。您可以增加该时间或循环等待，直到满足isTerminated() 条件：

executor.shutdown();
while (!executor.isTerminated()) {
    executor.awaitTermination(1, TimeUnit.SECONDS);
}