文件访问在Java对象上同步

class TableSaver {
    Timer timer = new Timer(true);

    TableSaver() {
        timer.schedule(new TableSaverTimerTask(),15000,SAVE_STATE_PERIOD);
    }

    synchronized TableColumns load(PersistentTable table) {
        String xml = loadFile(table.getTableKey());
        // parse XML,return
    }

    synchronized void save(String key,TableColumns value) {
        try {
            // Some preparations
            writeFile(app.getTableConfigFileName(key),xml);
        } catch (Exception e) {
            // ... handle
        }
    }

    private class TableSaverTimerTask extends TimerTask {
        @Override
        public void run() {
            synchronized (TableSaver.this) {
                Iterator<PersistentTable> iterator = queue.iterator();
                while (iterator.hasNext()) {
                    PersistentTable table = iterator.next();
                    if (table.getTableKey() != null) {
                        save(table.getTableKey(),dumpState(table));
                    }
                    iterator.remove();
                }
            }
        }
    }
}

>只存在一个TableSaver实例.
> load()可以从很多线程调用.计时器显然是另一个线程.
> loadFile()和writeFile()不会留下打开的文件流 – 它们使用一个健壮,经过良好测试和广泛使用的库,最终通过try …关闭流.

有时这样会失败,例如：

java.lang.RuntimeException: java.io.FileNotFoundException: C:pathtotable-MyTable.xml (The requested operation cannot be performed on a file with a user-mapped section open)
    at package.FileUtil.writeFile(FileUtil.java:33)
    at package.TableSaver.save(TableSaver.java:175)
    at package.TableSaver.access$600(TableSaver.java:34)
    at package.TableSaver$TableSaverTimerTask.run(TableSaver.java:246)
    at java.util.TimerThread.mainLoop(Unknown Source)
    at java.util.TimerThread.run(Unknown Source)
Caused by: java.io.FileNotFoundException: C:pathtotable-MyTable.xml (The requested operation cannot be performed on a file with a user-mapped section open)
    at java.io.FileOutputStream.open(Native Method)
    at java.io.FileOutputStream.<init>(Unknown Source)
    at java.io.FileOutputStream.<init>(Unknown Source)
    at package.FileUtilWorker.writeFile(FileUtilWorker.java:57)
    ... 6 more

所以我有两个问题：

>这种同步怎么会失败？请注意,我确定只有一个TableSaver实例.
> stacktrace中的这些东西是什么？package.TableSaver.access $600(TableSaver.java:34)？第34行是与类TableSaver {的行.这可能是同步不行的原因吗？