Class java.io.Reader 
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Class java.io.Reader 

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.

Version:
1.9, 98/07/01
Author:
Mark Reinhold
Since:
JDK1.1
See Also:
BufferedReader, LineNumberReader, CharArrayReader, InputStreamReader, FileReader, FilterReader, PushbackReader, PipedReader, StringReader, Writer

Variable Index

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

Constructor Index

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

Method Index

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

Variables

o lock 
protected java.lang.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.

Constructors

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

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

Methods

o 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
o 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
o markSupported 
public boolean markSupported()
Tell whether this stream supports the mark() operation.

o 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
o 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
o 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
o 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
o 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
o 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 
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