java.io
Class Reader

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

Direct Known Subclasses:

BufferedReader, CharArrayReader, FilterReader, InputStreamReader, PipedReader, StringReader, TextReader

public abstract class Reader

extends Object

Untamed: 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.

Since:

JDK1.1

Version:

1.23, 01/12/03

Author:

Mark Reinhold

See Also:

BufferedReader, LineNumberReader, CharArrayReader, InputStreamReader, FileReader, FilterReader, PushbackReader, PipedReader, StringReader, Writer

Field Summary

protected Object	lock The object used to synchronize operations on this stream.
private static int	maxSkipBufferSize Maximum skip-buffer size
private char[]	skipBuffer Skip buffer, null until allocated

Constructor Summary

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

Method Summary

abstract void	close() Enabled: Close the stream.
String	getText() Added: Gets the rest of the input as a String, normalizing newlines into '\n's.
Twine	getTwine(String url) Added: Gets the contents of the url as Twine (a text string that remembers where it came from), normalizing newlines into '\n's.
void	iterate(AssocFunc func) Added: Enumerates lineNumber => String (text line) associations.
void	iterate(AssocFunc func, String optURL) Added: Enumerates lineNumber => String/Twine (text line) associations.
void	mark(int readAheadLimit) Enabled: Mark the present position in the stream.
boolean	markSupported() Enabled: Tell whether this stream supports the mark() operation.
int	read() Enabled: Read a single character.
int	read(char[] cbuf) Enabled: Read characters into an array.
abstract int	read(char[] cbuf, int off, int len) Enabled: Read characters into a portion of an array.
Character	readChar() Added: Returns the next character, or null at end of file.
String	readString(int size) Added: Reads no more than 'size' characters from the file, and return them as a String.
boolean	ready() Enabled: Tell whether this stream is ready to be read.
void	reset() Enabled: Reset the stream.
long	skip(long n) Enabled: Skip characters.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

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.

maxSkipBufferSize

private static final int maxSkipBufferSize

Maximum skip-buffer size

skipBuffer

private char[] skipBuffer

Skip buffer, null until allocated

Constructor Detail

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.

Parameters:

lock - The Object to synchronize on.

Method Detail

read

public int read()
         throws IOException

Enabled: 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 65535 (0x00-0xffff), or -1 if the end of the stream has been reached

IOException

read

public int read(char[] cbuf)
         throws IOException

Enabled: 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 characters read, or -1 if the end of the stream has been reached

IOException

read

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

Enabled: 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

IOException

skip

public long skip(long n)
          throws IOException

Enabled: 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

IOException

ready

public boolean ready()
              throws IOException

Enabled: 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.

IOException

markSupported

public boolean markSupported()

Enabled: Tell whether this stream supports the mark() operation. The default implementation always returns false. Subclasses should override this method.

Returns:

true if and only if this stream supports the mark operation.

mark

public void mark(int readAheadLimit)
          throws IOException

Enabled: 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.

IOException

reset

public void reset()
           throws IOException

Enabled: 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().

IOException

close

public abstract void close()
                    throws IOException

Enabled: 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.

IOException

readChar

public Character readChar()
                   throws IOException

Added: Returns the next character, or null at end of file.

IOException

iterate

public void iterate(AssocFunc func,
                    String optURL)
             throws IOException

Added: Enumerates lineNumber => String/Twine (text line) associations.

Each text line ends with a "\n".

IOException

iterate

public void iterate(AssocFunc func)
             throws IOException

Added: Enumerates lineNumber => String (text line) associations.

Each text line ends with a "\n". optURL defaults to null.

IOException

getText

public String getText()
               throws IOException

Added: Gets the rest of the input as a String, normalizing newlines into '\n's.

IOException

getTwine

public Twine getTwine(String url)
               throws IOException

Added: Gets the contents of the url as Twine (a text string that remembers where it came from), normalizing newlines into '\n's.

IOException

readString

public String readString(int size)
                  throws IOException

Added: Reads no more than 'size' characters from the file, and return them as a String. If at end-of-file, return null.

IOException