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Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class PushbackReader - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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java.io
Class PushbackReader

java.lang.Object
  |
  +--java.io.Reader
        |
        +--java.io.FilterReader
              |
              +--java.io.PushbackReader
public class PushbackReader
extends FilterReader

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

Since:
JDK1.1

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.
 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.FilterReader
skip
 
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
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