Class PushbackReader

java.lang.Object

java.io.Reader

java.io.FilterReader

java.io.PushbackReader

All Implemented Interfaces:

Closeable, AutoCloseable, Readable

public class PushbackReader
extends FilterReader

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

Since:

1.1

Field Summary

Fields declared in class FilterReader

in

Modifier and Type	Field	Description
protected Reader	in	The underlying character-input stream.

Fields declared in class Reader

lock

Modifier and Type	Field	Description
protected Object	lock	The object used to synchronize operations on this stream.

Constructor Summary

Constructors

Constructor	Description
PushbackReader(Reader in)	Creates a new pushback reader with a one-character pushback buffer.
PushbackReader(Reader in, int size)	Creates a new pushback reader with a pushback buffer of the given size.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes the stream and releases any system resources associated with it.
void	mark(int readAheadLimit)	Marks the present position in the stream.
boolean	markSupported()	Tells whether this stream supports the mark() operation, which it does not.
int	read()	Reads a single character.
boolean	ready()	Tells whether this stream is ready to be read.
void	reset()	Resets the stream.
void	unread(char[] cbuf)	Pushes back an array of characters by copying it to the front of the pushback buffer.
void	unread(char[] cbuf, int off, int len)	Pushes back a portion of an array of characters by copying it to the front of the pushback buffer.
void	unread(int c)	Pushes back a single character by copying it to the front of the pushback buffer.

Methods declared in class FilterReader

read, skip

Modifier and Type	Method	Description
int	read(char[] cbuf, int off, int len)	Reads characters into a portion of an array.
long	skip(long n)	Skips characters.

Methods declared in class Reader

nullReader, of, read, read, readAllAsString, readAllLines, transferTo

Modifier and Type	Method	Description
static Reader	nullReader()	Returns a new Reader that reads no characters.
static Reader	of(CharSequence cs)	Returns a Reader that reads characters from a CharSequence.
int	read(char[] cbuf)	Reads characters into an array.
int	read(CharBuffer target)	Attempts to read characters into the specified character buffer.
String	readAllAsString()	Reads all remaining characters into a string.
List<String>	readAllLines()	Reads all remaining characters as lines of text.
long	transferTo(Writer out)	Reads all characters from this reader and writes the characters to the given writer in the order that they are read.

Methods declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Constructor Details

PushbackReader

public PushbackReader(Reader in,
 int size)

Creates 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 <= 0

PushbackReader

public PushbackReader(Reader in)

Creates a new pushback reader with a one-character pushback buffer.

Parameters:

in - The reader from which characters will be read

Method Details

read

public int read()
         throws IOException

Reads 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

unread

public void unread(int c)
            throws IOException

Pushes back a single character by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value (char)c.

Parameters:

c - The int value representing a character to be pushed 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

Pushes 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

Pushes 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

Tells whether this stream is ready to be read.

Overrides:

ready in class FilterReader

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

mark

public void mark(int readAheadLimit)
          throws IOException

Marks the present position in the stream. The mark for class PushbackReader always throws an exception.

Overrides:

mark in class FilterReader

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 - Always, since mark is not supported

reset

public void reset()
           throws IOException

Resets 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()

Tells whether this stream supports the mark() operation, which it does not.

Overrides:

markSupported in class FilterReader

Returns:

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

close

public void close()
           throws IOException

Closes the stream and releases any system resources associated with it. Once the stream has been closed, further read(), unread(), ready(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect. This method will block while there is another thread blocking on the reader.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in class Reader

Throws:

IOException - If an I/O error occurs