Попробуй для проверки запустить вот это:
| Код |
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
public class Locking {
public static void main(String args[]) throws IOException {
if (args.length == 0)
System.out.println("Use \"java Locking filename\"");
else {
FileChannel channel = new RandomAccessFile(args[0], "rw").getChannel();
FileLock lock = channel.lock();//or channel.tryLock(); lock() return FileLock
try {
System.out.println("GOT LOCK");
System.out.println("Now you can try edit or delete file \"" + args[0] + "\"");
System.out.println("Press ENTER to continue");
System.in.read(new byte[10]);
} finally {
System.out.println("RELEASED LOCK");
lock.release();
channel.close();
}
System.out.println("OK");
}
}
}
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Цитата(Bulat @ 29.5.2006, 14:04  ) | | Что там делается lock я не понял........ |
Вот что написано в Thinking in Java 3 Edition:
| Цитата |
File locking, introduced in JDK 1.4, allows you to synchronize access to a file as a shared resource. However, the two threads that contend for the same file may be in different JVMs, or one may be a Java thread and the other some native thread in the operating system. The file locks are visible to other operating system processes because Java file locking maps directly to the native operating system locking facility.
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You get a FileLock on the entire file by calling either tryLock( ) or lock( ) on a FileChannel. (SocketChannel, DatagramChannel, and ServerSocketChannel do not need locking since they are inherently single-process entities; you don’t generally share a network socket between two processes.) tryLock( ) is non-blocking. It tries to grab the lock, but if it cannot (when some other process already holds the same lock and it is not shared), it simply returns from the method call. lock( ) blocks until the lock is acquired, or the thread that invoked lock( ) is interrupted, or the channel on which the lock( ) method is called is closed. A lock is released using FileLock.release( ).
It is also possible to lock a part of the file by using
tryLock(long position, long size, boolean shared)
or
lock(long position, long size, boolean shared)
which locks the region (size - position). The third argument specifies whether this lock is shared. Feedback
Although the zero-argument locking methods adapt to changes in the size of a file, locks with a fixed size do not change if the file size changes. If a lock is acquired for a region from position to position+size and the file increases beyond position+size, then the section beyond position+size is not locked. The zero-argument locking methods lock the entire file, even if it grows. Feedback
Support for exclusive or shared locks must be provided by the underlying operating system. If the operating system does not support shared locks and a request is made for one, an exclusive lock is used instead. The type of lock (shared or exclusive) can be queried using FileLock.isShared( )
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