Examples of java.nio.channels.FileChannel.tryLock()

java.nio.channels.FileChannel.tryLock()
Attempts to acquire an exclusive lock on this file without blocking.
This is a convenience method for attempting to acquire a maximum length lock on the file. It is equivalent to:
```
 fileChannel.tryLock(0L, Long.MAX_VALUE, false) 
```
The method returns null if the acquisition would result in an overlapped lock with another OS process.
@return the file lock object, or null if the lock wouldoverlap an existing exclusive lock in another OS process. @throws ClosedChannelException the file channel is closed. @throws OverlappingFileLockException Either a lock is already held that overlaps this lock request, or another thread is waiting to acquire a lock that will overlap with this request. @throws IOException if any I/O error occurs

            lockFile.deleteOnExit();


            @SuppressWarnings("resource")
            FileOutputStream out = new FileOutputStream(lockFile);
            FileChannel channel = out.getChannel();
            _fileLock = channel.tryLock();
        }
        catch (IOException ioe)
        {
            throw new StoreException("Cannot create the lock file " + lockFile.getName(), ioe);
        }

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                    }
                }


                // get the lock using either try lock or not depending on if we are using timeout or not
                try {
                    lock = timeout > 0 ? channel.tryLock() : channel.lock();
                } catch (IllegalStateException ex) {
                    // Also catch the OverlappingFileLockException here. Do nothing here                    
                }
                if (lock != null) {
                    LOG.trace("Acquired exclusive read lock: {} to file: {}", lock, target);

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        try {
            if ((!file.exists()) || file.canWrite()) {
                try {
                    raf = new RandomAccessFile(file, "rw");
                    final FileChannel channel = raf.getChannel();   
                    final FileLock lock = channel.tryLock();
                    if (lock == null)
                        {readOnly = true;}
                //TODO : who will release the lock ? -pb
                } catch (final NonWritableChannelException e) {
                    //No way : switch to read-only mode

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                lockFile.createNewFile();
                lockFile.deleteOnExit();
            }


            FileChannel lockChannel = new FileOutputStream(lockFile).getChannel();
            lock = lockChannel.tryLock();
        } catch (IOException e)
        {
            LOG.log(Level.WARNING, "Unable to create lock", e);
        }

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      try {
        channel = new RandomAccessFile(file, "rw").getChannel();


        // Use the file channel to create a lock on the file.
        // This method blocks until it can retrieve the lock.
        FileLock lock = channel.tryLock();
        if (lock == null) {
          // could not get lock - means some other instance is locking the file
          return true;
        }
        lock.release();

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                    }
                }


                // get the lock using either try lock or not depending on if we are using timeout or not
                try {
                    lock = timeout > 0 ? channel.tryLock() : channel.lock();
                } catch (IllegalStateException ex) {
                    // Also catch the OverlappingFileLockException here. Do nothing here                    
                }
                if (lock != null) {
                    if (LOG.isTraceEnabled()) {

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            {
                _storeRAF = new RandomAccessFile(_storeFile, "rw");
                FileChannel fileChannel = _storeRAF.getChannel();
                try
                {
                    _storeLock = fileChannel.tryLock();
                }
                catch (OverlappingFileLockException e)
                {
                    _storeLock = null;
                }

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            lockFile.deleteOnExit();


            @SuppressWarnings("resource")
            FileOutputStream out = new FileOutputStream(lockFile);
            FileChannel channel = out.getChannel();
            _fileLock = channel.tryLock();
        }
        catch (IOException ioe)
        {
            throw new StoreException("Cannot create the lock file " + lockFile.getName(), ioe);
        }

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                runtimeDirectory = "";
            }
            for (int i = 2;; i++) { // Try current directory, then "runtime2/", "runtime3/", etc.
                RandomAccessFile raf = new RandomAccessFile(runtimeDirectory + "lockfile.lck", "rw");
                FileChannel fc = raf.getChannel();
                pathLock = fc.tryLock();
                if (pathLock != null) {
                    break;
                }
                runtimeDirectory = "runtime" + i + "/"; // Construct a subdirectory name "runtime2/", "runtime3/", etc.
            }

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    public boolean lockComponent(String name) throws FileNotFoundException {
        File file = lockFile(name);
        RandomAccessFile raf = new RandomAccessFile(file, "rwd");
        FileChannel channel = raf.getChannel();
        try {
            FileLock l = channel.tryLock();
            if (l == null) {
                Execute.close(channel);
                return false;
            }
            file.deleteOnExit();

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