JavaTM 2 Platform
Std. Ed. v1.4.2

java.io
Class PushbackReader

java.lang.Object
  extended byjava.io.Reader
      extended byjava.io.FilterReader
          extended byjava.io.PushbackReader

public class PushbackReader
extends FilterReader

A character-stream reader that allows characters to be pushed back into the stream.

Since:
JDK1.1

Field Summary
 
Fields inherited from class java.io.FilterReader
in
 
Fields inherited from class java.io.Reader
lock
 
Constructor Summary
PushbackReader(Reader in)
          Create a new pushback reader with a one-character pushback buffer.
PushbackReader(Reader in, int size)
          Create a new pushback reader with a pushback buffer of the given size.
 
Method Summary
 void close()
          Close the stream.
 void mark(int readAheadLimit)
          Mark the present position in the stream.
 boolean markSupported()
          Tell whether this stream supports the mark() operation, which it does not.
 int read()
          Read a single character.
 int read(char[] cbuf, int off, int len)
          Read characters into a portion of an array.
 boolean ready()
          Tell whether this stream is ready to be read.
 void reset()
          Reset the stream.
 long skip(long n)
          Skip characters.
 void unread(char[] cbuf)
          Push back an array of characters by copying it to the front of the pushback buffer.
 void unread(char[] cbuf, int off, int len)
          Push back a portion of an array of characters by copying it to the front of the pushback buffer.
 void unread(int c)
          Push back a single character.
 
Methods inherited from class java.io.Reader
read
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

PushbackReader

public PushbackReader(Reader in,
                      int size)
Create a new pushback reader with a pushback buffer of the given size.

Parameters:
in - The reader from which characters will be read
size - The size of the pushback buffer
Throws:
IllegalArgumentException - if size is <= 0

PushbackReader

public PushbackReader(Reader in)
Create a new pushback reader with a one-character pushback buffer.

Parameters:
in - The reader from which characters will be read
Method Detail

read

public int read()
         throws IOException
Read a single character.

Overrides:
read in class FilterReader
Returns:
The character read, 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,
                int off,
                int len)
         throws IOException
Read characters into a portion of an array.

Overrides:
read in class FilterReader
Parameters:
cbuf - Destination buffer
off - Offset at which to start writing 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

unread

public void unread(int c)
            throws IOException
Push back a single character.

Parameters:
c - The character to push back
Throws:
IOException - If the pushback buffer is full, or if some other I/O error occurs

unread

public void unread(char[] cbuf,
                   int off,
                   int len)
            throws IOException
Push back a portion of an array of characters by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value cbuf[off], the character after that will have the value cbuf[off+1], and so forth.

Parameters:
cbuf - Character array
off - Offset of first character to push back
len - Number of characters to push back
Throws:
IOException - If there is insufficient room in the pushback buffer, or if some other I/O error occurs

unread

public void unread(char[] cbuf)
            throws IOException
Push back an array of characters by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value cbuf[0], the character after that will have the value cbuf[1], and so forth.

Parameters:
cbuf - Character array to push back
Throws:
IOException - If there is insufficient room in the pushback buffer, or if some other I/O error occurs

ready

public boolean ready()
              throws IOException
Tell whether this stream is ready to be read.

Overrides:
ready in class FilterReader
Throws:
IOException - If an I/O error occurs

mark

public void mark(int readAheadLimit)
          throws IOException
Mark the present position in the stream. The mark for class PushbackReader always throws an exception.

Overrides:
mark in class FilterReader
Throws:
IOException - Always, since mark is not supported

reset

public void reset()
           throws IOException
Reset the stream. The reset method of PushbackReader always throws an exception.

Overrides:
reset in class FilterReader
Throws:
IOException - Always, since reset is not supported

markSupported

public boolean markSupported()
Tell whether this stream supports the mark() operation, which it does not.

Overrides:
markSupported in class FilterReader

close

public void close()
           throws IOException
Close the stream.

Overrides:
close in class FilterReader
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.

Overrides:
skip in class FilterReader
Parameters:
n - The number of characters to skip
Returns:
The number of characters actually skipped
Throws:
IllegalArgumentException - If n is negative.
IOException - If an I/O error occurs

JavaTM 2 Platform
Std. Ed. v1.4.2

Submit a bug or feature
For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2003 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.


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