从多个线程可靠地写入一个 PrintWriter

发布于 2024-12-10 03:47:18 字数 667 浏览 0 评论 0原文

我遇到了一个问题，我有多个线程写入同一个 PrintWriter，但并非所有数据都写入文件。我知道多线程部分工作正常，因为我可以将所有内容打印到控制台。同步写入语句似乎不起作用。可能是什么问题？

ExecutorService pool = Executors.newFixedThreadPool(poolSize);

for (Integer i : map.keySet()) {
    final Collection<String[]> set = map.get(i);
    pool.submit(new Runnable() {
        public void run() {
        StringBuffer sb = Matcher.performCollectionMatch(params);
        synchronized (this) {
            resultFile.print(sb); //this is a PrintWriter - it does NOT capture all sb
            resultFile.flush();
            System.out.print(sb); //this actually prints out ALL sb
        }
        }
    });
} //FOR loop

原文

I'm running into an issue where I have multiple threads that write to the same PrintWriter and not all the data is getting written to the file. I know the multi-threaded part is working correctly since I can print everything to the console. Synchronizing the write statements does not seem to be working. What could be the problem?

ExecutorService pool = Executors.newFixedThreadPool(poolSize);

for (Integer i : map.keySet()) {
    final Collection<String[]> set = map.get(i);
    pool.submit(new Runnable() {
        public void run() {
        StringBuffer sb = Matcher.performCollectionMatch(params);
        synchronized (this) {
            resultFile.print(sb); //this is a PrintWriter - it does NOT capture all sb
            resultFile.flush();
            System.out.print(sb); //this actually prints out ALL sb
        }
        }
    });
} //FOR loop

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征棹 2024-12-17 03:47:18

为了使同步工作正常，您应该为所有线程使用相同的对象，例如：

...
synchronized (resultFile) {
...

For synchronization to work, you should use the same object for all threads, e.g.:

...
synchronized (resultFile) {
...

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临风闻羌笛 2024-12-17 03:47:18

池停止后是否关闭 PrintWriter ？

pool.shutdown();
final boolean terminated = pool.awaitTermination(8, TimeUnit.SECONDS);
if (!terminated) {
    throw new IllegalStateException("pool shutdown timeout");
}

resultFile.close();

Do you close the PrintWriter after the pool stops?

pool.shutdown();
final boolean terminated = pool.awaitTermination(8, TimeUnit.SECONDS);
if (!terminated) {
    throw new IllegalStateException("pool shutdown timeout");
}

resultFile.close();

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意中人 2024-12-17 03:47:18

一种更简单的解决方案是确保池中只有一个线程。这样您就不需要同步写入，因为只有一个线程。

ExecutorService pool = Executors.newSingleThreadedPool();

for (Integer i : map.keySet()) {
    final Collection<String[]> set = map.get(i);
    pool.executor(new Runnable() {
        public void run() {
            StringBuilder sb = Matcher.performCollectionMatch(params);
            resultFile.print(sb); //this is a PrintWriter - it does NOT capture all sb 
            System.out.print(sb); //this actually prints out ALL sb
        }
    });
} //FOR loop

瓶颈很可能是磁盘访问，因此添加更多线程可能没有帮助。

A simpler solution is to ensure there is only one thread in the pool. This way you don't need to synchonize writing as there is only one thread.

ExecutorService pool = Executors.newSingleThreadedPool();

for (Integer i : map.keySet()) {
    final Collection<String[]> set = map.get(i);
    pool.executor(new Runnable() {
        public void run() {
            StringBuilder sb = Matcher.performCollectionMatch(params);
            resultFile.print(sb); //this is a PrintWriter - it does NOT capture all sb 
            System.out.print(sb); //this actually prints out ALL sb
        }
    });
} //FOR loop

It is quite likely the bottle neck is you disk access so adding more threads may not help.

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~没有更多了~