Class java.io.Reader - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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Class java.io.Reader

java.lang.Object
   |
   +----java.io.Reader

public abstract class Reader
extends Object

Abstract class for reading character streams. The only methods that a subclass must implement are read(char[], int, int) and close(). Most subclasses, however, will override some of the methods defined here in order to provide higher efficiency, additional functionality, or both.

See Also:: BufferedReader, LineNumberReader, CharArrayReader, InputStreamReader, FileReader, FilterReader, PushbackReader, PipedReader, StringReader, Writer

lock: The object used to synchronize operations on this stream.

Reader(): Create a new character-stream reader whose critical sections will synchronize on the reader itself.
Reader(Object): Create a new character-stream reader whose critical sections will synchronize on the given object.

close(): Close the stream.
mark(int): Mark the present position in the stream.
markSupported(): Tell whether this stream supports the mark() operation.
read(): Read a single character.
read(char[]): Read characters into an array.
read(char[], int, int): Read characters into a portion of an array.
ready(): Tell whether this stream is ready to be read.
reset(): Reset the stream.
skip(long): Skip characters.

lock

 protected Object lock

The object used to synchronize operations on this stream. For efficiency, a character-stream object may use an object other than itself to protect critical sections. A subclass should therefore use the object in this field rather than this or a synchronized method.

Reader

 protected Reader()

Create a new character-stream reader whose critical sections will synchronize on the reader itself.

Reader

 protected Reader(Object lock)

Create a new character-stream reader whose critical sections will synchronize on the given object.

read

 public int read() throws IOException

Read a single character. This method will block until a character is available, an I/O error occurs, or the end of the stream is reached.

Subclasses that intend to support efficient single-character input should override this method.

Returns:: The character read, as an integer in the range 0 to 16383 (0x00-0xffff), or -1 if the end of the stream has been reached
Throws: IOException: If an I/O error occurs

read

 public int read(char cbuf[]) throws IOException

Read characters into an array. This method will block until some input is available, an I/O error occurs, or the end of the stream is reached.

Parameters:: cbuf - Destination buffer
Returns:: The number of bytes read, or -1 if the end of the stream has been reached
Throws: IOException: If an I/O error occurs

read

 public abstract int read(char cbuf[],
                          int off,
                          int len) throws IOException

Read characters into a portion of an array. This method will block until some input is available, an I/O error occurs, or the end of the stream is reached.

Parameters:: cbuf - Destination buffer; off - Offset at which to start storing characters; len - Maximum number of characters to read
Returns:: The number of characters read, or -1 if the end of the stream has been reached
Throws: IOException: If an I/O error occurs

skip

 public long skip(long n) throws IOException

Skip characters. This method will block until some characters are available, an I/O error occurs, or the end of the stream is reached.

Parameters:: n - The number of characters to skip
Returns:: The number of characters actually skipped
Throws: IOException: If an I/O error occurs

ready

 public boolean ready() throws IOException

Tell whether this stream is ready to be read.

Returns:: True if the next read() is guaranteed not to block for input, false otherwise. Note that returning false does not guarantee that the next read will block.
Throws: IOException: If an I/O error occurs

markSupported

 public boolean markSupported()

Tell whether this stream supports the mark() operation.

mark

 public void mark(int readAheadLimit) throws IOException

Mark the present position in the stream. Subsequent calls to reset() will attempt to reposition the stream to this point. Not all character-input streams support the mark() operation.

Parameters:: readAheadLimit - Limit on the number of characters that may be read while still preserving the mark. After reading this many characters, attempting to reset the stream may fail.
Throws: IOException: If the stream does not support mark(), or if some other I/O error occurs

reset

 public void reset() throws IOException

Reset the stream. If the stream has been marked, then attempt to reposition it at the mark. If the stream has not been marked, then attempt to reset it in some way appropriate to the particular stream, for example by repositioning it to its starting point. Not all character-input streams support the reset() operation, and some support reset() without supporting mark().

Throws: IOException: If the stream has not been marked, or if the mark has been invalidated, or if the stream does not support reset(), or if some other I/O error occurs

close

 public abstract void close() throws IOException

Close the stream. Once a stream has been closed, further read(), ready(), mark(), or reset() invocations will throw an IOException. Closing a previously-closed stream, however, has no effect.

Throws: IOException: If an I/O error occurs

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