FileChannel

Protected default constructor.

Requests that all updates to this channel are committed to the storage device.

When this method returns, all modifications made to the platform file underlying this channel have been committed if the file resides on a local storage device. If the file is not hosted locally, for example on a networked file system, then applications cannot be certain that the modifications have been committed.

There are no assurances given that changes made to the file using methods defined elsewhere will be committed. For example, changes made via a mapped byte buffer may not be committed.

The metadata parameter indicates whether the update should include the file's metadata such as last modification time, last access time, etc. Note that passing true may invoke an underlying write to the operating system (if the platform is maintaining metadata such as last access time), even if the channel is opened read-only.

Obtains a lock on a specified region of the file.

This is the blocking version of lock acquisition, see also the tryLock() methods.

Attempts to acquire an overlapping lock region will fail. The attempt will fail if the overlapping lock has already been obtained, or if another thread is currently waiting to acquire the overlapping lock.

If the request is not for an overlapping lock, the thread calling this method will block until the lock is obtained (likely by no contention or another process releasing a lock), or until this thread is interrupted or the channel is closed.

If the lock is obtained successfully then the FileLock object returned represents the lock for subsequent operations on the locked region.

If the thread is interrupted while waiting for the lock, the thread is set to the interrupted state and throws a FileLockInterruptionException. If this channel is closed while the thread is waiting to obtain the lock then the thread throws a AsynchronousCloseException.

There is no requirement for the position and size to be within the current start and length of the file.

Some platforms do not support shared locks, and if a request is made for a shared lock on such a platform, this method will attempt to acquire an exclusive lock instead. It is undefined whether the lock obtained is advisory or mandatory.

Obtains an exclusive lock on this file.

This is a convenience method for acquiring a maximum length lock on a file. It is equivalent to: fileChannel.lock(0L, Long.MAX_VALUE, false);

Maps the file into memory. There can be three modes: read-only, read/write and private. After mapping, changes made to memory or the file channel do not affect the other storage place.

Note: mapping a file into memory is usually expensive.

Returns the current value of the file position pointer.

Sets the file position pointer to a new value.

The argument is the number of bytes counted from the start of the file. The position cannot be set to a value that is negative. The new position can be set beyond the current file size. If set beyond the current file size, attempts to read will return end of file. Write operations will succeed but they will fill the bytes between the current end of file and the new position with the required number of (unspecified) byte values.

Reads bytes from this file channel into a subset of the given buffers. This method attempts to read all remaining() bytes from length byte buffers, in order, starting at targets[offset]. It increases the file position by the number of bytes actually read. The number of bytes actually read is returned.

If a read operation is in progress, subsequent threads will block until the read is completed and will then contend for the ability to read.

Reads bytes from this file channel into the given buffer.

The maximum number of bytes that will be read is the remaining number of bytes in the buffer when the method is invoked. The bytes will be copied into the buffer starting at the buffer's current position.

The call may block if other threads are also attempting to read from this channel.

Upon completion, the buffer's position is set to the end of the bytes that have been read. The buffer's limit is not changed.

Reads bytes from this file channel into the given buffer starting from the specified file position.

The bytes are read starting at the given file position (up to the remaining number of bytes in the buffer). The number of bytes actually read is returned.

If position is beyond the current end of file, then no bytes are read.

Note that the file position is unmodified by this method.

Reads bytes from this file channel and stores them in the specified array of buffers. This method attempts to read as many bytes as can be stored in the buffer array from this channel and returns the number of bytes actually read. It also increases the file position by the number of bytes read.

If a read operation is in progress, subsequent threads will block until the read is completed and will then contend for the ability to read.

Calling this method is equivalent to calling read(buffers, 0, buffers.length);

Returns the size of the file underlying this channel in bytes.

Reads up to count bytes from src and stores them in this channel's file starting at position. No bytes are transferred if position is larger than the size of this channel's file. Less than count bytes are transferred if there are less bytes remaining in the source channel or if the source channel is non-blocking and has less than count bytes immediately available in its output buffer.

Note that this channel's position is not modified.

Reads up to count bytes from this channel's file starting at position and writes them to target. No bytes are transferred if position is larger than the size of this channel's file. Less than count bytes are transferred if there less bytes available from this channel's file or if the target channel is non-blocking and has less than count bytes free in its input buffer.

Note that this channel's position is not modified.

Truncates the file underlying this channel to a given size. Any bytes beyond the given size are removed from the file. If there are no bytes beyond the given size then the file contents are unmodified.

If the file position is currently greater than the given size, then it is set to the new size.

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.

Attempts to acquire an exclusive lock on this file without blocking. The method returns null if the acquisition would result in an overlapped lock with another OS process.

It is possible to acquire a lock for any region even if it's completely outside of the file's size. The size of the lock is fixed. If the file grows outside of the lock that region of the file won't be locked by this lock.

Attempts to write a subset of the given bytes from the buffers to this file channel. This method attempts to write all remaining() bytes from length byte buffers, in order, starting at sources[offset]. The number of bytes actually written is returned.

If a write operation is in progress, subsequent threads will block until the write is completed and then contend for the ability to write.

Writes bytes from the given buffer to this file channel starting at the given file position.

The bytes are written starting at the given file position (up to the remaining number of bytes in the buffer). The number of bytes actually written is returned.

If the position is beyond the current end of file, then the file is first extended up to the given position by the required number of unspecified byte values.

Note that the file position is not modified by this method.

Writes bytes from all the given byte buffers to this file channel.

The bytes are written starting at the current file position, and after the bytes are written (up to the remaining number of bytes in all the buffers), the file position is increased by the number of bytes actually written.

Calling this method is equivalent to calling write(buffers, 0, buffers.length);

Writes bytes from the given byte buffer to this file channel.

The bytes are written starting at the current file position, and after some number of bytes are written (up to the remaining number of bytes in the buffer) the file position is increased by the number of bytes actually written.