SeekableByteChannel

所有超级接口:

AutoCloseable, ByteChannel, Channel, Closeable, ReadableByteChannel, WritableByteChannel

所有已知实现类:

FileChannel
```
public interface SeekableByteChannel
extends ByteChannel
```
A byte channel that maintains a current position and allows the position to be changed.
A seekable byte channel is connected to an entity, typically a file, that contains a variable-length sequence of bytes that can be read and written. The current position can be queried and modified. The channel also provides access to the current size of the entity to which the channel is connected. The size increases when bytes are written beyond its current size; the size decreases when it is truncated.
The position and truncate methods which do not otherwise have a value to return are specified to return the channel upon which they are invoked. This allows method invocations to be chained. Implementations of this interface should specialize the return type so that method invocations on the implementation class can be chained.

从以下版本开始:

1.7

另请参阅:

Files.newByteChannel(java.nio.file.Path, java.util.Set<? extends java.nio.file.OpenOption>, java.nio.file.attribute.FileAttribute<?>...)

方法概要

所有方法实例方法抽象方法
限定符和类型	方法	说明
`long`	`position()`	Returns this channel's position.
`SeekableByteChannel`	`position(long newPosition)`	Sets this channel's position.
`int`	`read(ByteBuffer dst)`	Reads a sequence of bytes from this channel into the given buffer.
`long`	`size()`	Returns the current size of entity to which this channel is connected.
`SeekableByteChannel`	`truncate(long size)`	Truncates the entity, to which this channel is connected, to the given size.
`int`	`write(ByteBuffer src)`	Writes a sequence of bytes to this channel from the given buffer.

从接口继承的方法 java.nio.channels.Channel
close, isOpen

- 方法详细资料
  - 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.
    
    指定者:
    
    read 在接口中 ReadableByteChannel
    
    参数:
    
    dst - The buffer into which bytes are to be transferred
    
    返回:
    
    The number of bytes read, possibly zero, or -1 if the channel has reached end-of-stream
    
    抛出:
    
    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.
    
    指定者:
    
    write 在接口中 WritableByteChannel
    
    参数:
    
    src - The buffer from which bytes are to be retrieved
    
    返回:
    
    The number of bytes written, possibly zero
    
    抛出:
    
    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.
    
    返回:
    
    This channel's position, a non-negative integer counting the number of bytes from the beginning of the entity to the current position
    
    抛出:
    
    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.
    
    参数:
    
    newPosition - The new position, a non-negative integer counting the number of bytes from the beginning of the entity
    
    返回:
    
    This channel
    
    抛出:
    
    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.
    
    返回:
    
    The current size, measured in bytes
    
    抛出:
    
    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.
    
    参数:
    
    size - The new size, a non-negative byte count
    
    返回:
    
    This channel
    
    抛出:
    
    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

接口 SeekableByteChannel

方法概要

从接口继承的方法 java.nio.channels.Channel

方法详细资料

read

write

position

position

size

truncate