Java compact1, compact2, compact3 java.nio.channels Interface SeekableByteChannel（JDK8）

Method Detail

• read

  int read(ByteBuffer dst)
    throws IOException

  Reads a sequence of bytes from this channel into the given buffer.

  Bytes are read starting at this channel's current position, and then the position is updated with the number of bytes actually read. Otherwise this method behaves exactly as specified in the ReadableByteChannel interface.

  Specified by:

  read in interface ReadableByteChannel

  Parameters:

  dst - The buffer into which bytes are to be transferred

  Returns:

  The number of bytes read, possibly zero, or -1 if the channel has reached end-of-stream

  Throws:

  ClosedChannelException - If this channel is closed

  AsynchronousCloseException - If another thread closes this channel while the read operation is in progress

  ClosedByInterruptException - If another thread interrupts the current thread while the read operation is in progress, thereby closing the channel and setting the current thread's interrupt status

  IOException - If some other I/O error occurs

• write

  int write(ByteBuffer src)
     throws IOException

  Writes a sequence of bytes to this channel from the given buffer.

  Bytes are written starting at this channel's current position, unless the channel is connected to an entity such as a file that is opened with the APPEND option, in which case the position is first advanced to the end. The entity to which the channel is connected is grown, if necessary, to accommodate the written bytes, and then the position is updated with the number of bytes actually written. Otherwise this method behaves exactly as specified by the WritableByteChannel interface.

  Specified by:

  write in interface WritableByteChannel

  Parameters:

  src - The buffer from which bytes are to be retrieved

  Returns:

  The number of bytes written, possibly zero

  Throws:

  ClosedChannelException - If this channel is closed

  AsynchronousCloseException - If another thread closes this channel while the write operation is in progress

  ClosedByInterruptException - If another thread interrupts the current thread while the write operation is in progress, thereby closing the channel and setting the current thread's interrupt status

  IOException - If some other I/O error occurs

• position

  long position()
         throws IOException

  Returns this channel's position.

  Returns:

  This channel's position, a non-negative integer counting the number of bytes from the beginning of the entity to the current position

  Throws:

  ClosedChannelException - If this channel is closed

  IOException - If some other I/O error occurs

• position

  SeekableByteChannel position(long newPosition)
                        throws IOException

  Sets this channel's position.

  Setting the position to a value that is greater than the current size is legal but does not change the size of the entity. A later attempt to read bytes at such a position will immediately return an end-of-file indication. A later attempt to write bytes at such a position will cause the entity to grow to accommodate the new bytes; the values of any bytes between the previous end-of-file and the newly-written bytes are unspecified.

  Setting the channel's position is not recommended when connected to an entity, typically a file, that is opened with the APPEND option. When opened for append, the position is first advanced to the end before writing.

  Parameters:

  newPosition - The new position, a non-negative integer counting the number of bytes from the beginning of the entity

  Returns:

  This channel

  Throws:

  ClosedChannelException - If this channel is closed

  IllegalArgumentException - If the new position is negative

  IOException - If some other I/O error occurs

• size

  long size()
     throws IOException

  Returns the current size of entity to which this channel is connected.

  Returns:

  The current size, measured in bytes

  Throws:

  ClosedChannelException - If this channel is closed

  IOException - If some other I/O error occurs

• truncate

  SeekableByteChannel truncate(long size)
                        throws IOException

  Truncates the entity, to which this channel is connected, to the given size.

  If the given size is less than the current size then the entity is truncated, discarding any bytes beyond the new end. If the given size is greater than or equal to the current size then the entity is not modified. In either case, if the current position is greater than the given size then it is set to that size.

  An implementation of this interface may prohibit truncation when connected to an entity, typically a file, opened with the APPEND option.

  Parameters:

  size - The new size, a non-negative byte count

  Returns:

  This channel

  Throws:

  NonWritableChannelException - If this channel was not opened for writing

  ClosedChannelException - If this channel is closed

  IllegalArgumentException - If the new size is negative

  IOException - If some other I/O error occurs