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PushbackReader

public class PushbackReader
extends FilterReader

java.lang.Object
   ↳ java.io.Reader
     ↳ java.io.FilterReader
       ↳ java.io.PushbackReader


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

Summary

Inherited fields

Public constructors

PushbackReader(Reader in, int size)

Creates a new pushback reader with a pushback buffer of the given size.

PushbackReader(Reader in)

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

Public methods

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.

int read(char[] cbuf, int off, int len)

Reads characters into a portion of an array.

boolean ready()

Tells whether this stream is ready to be read.

void reset()

Resets the stream.

long skip(long n)

Skips characters.

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(char[] cbuf)

Pushes back 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.

Inherited methods

Public constructors

PushbackReader

added in API level 1
public PushbackReader (Reader in, 
                int size)

Creates a new pushback reader with a pushback buffer of the given size.

Parameters
in Reader: The reader from which characters will be read

size int: The size of the pushback buffer

Throws
IllegalArgumentException if size <= 0

PushbackReader

added in API level 1
public PushbackReader (Reader in)

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

Parameters
in Reader: The reader from which characters will be read

Public methods

close

added in API level 1
public void close ()

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.

Throws
IOException If an I/O error occurs

mark

added in API level 1
public void mark (int readAheadLimit)

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

Parameters
readAheadLimit int: 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

markSupported

added in API level 1
public boolean markSupported ()

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

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

read

added in API level 1
public int read ()

Reads a single character.

Returns
int The character read, or -1 if the end of the stream has been reached

Throws
IOException If an I/O error occurs

read

added in API level 1
public int read (char[] cbuf, 
                int off, 
                int len)

Reads characters into a portion of an array.

Parameters
cbuf char: Destination buffer

off int: Offset at which to start writing characters

len int: Maximum number of characters to read

Returns
int The number of characters read, or -1 if the end of the stream has been reached

Throws
IOException If an I/O error occurs

ready

added in API level 1
public boolean ready ()

Tells whether this stream is ready to be read.

Returns
boolean 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

reset

added in API level 1
public void reset ()

Resets the stream. The reset method of PushbackReader always throws an exception.

Throws
IOException Always, since reset is not supported

skip

added in API level 1
public long skip (long n)

Skips 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 long: The number of characters to skip

Returns
long The number of characters actually skipped

Throws
IllegalArgumentException If n is negative.
IOException If an I/O error occurs

unread

added in API level 1
public 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. 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 char: Character array

off int: Offset of first character to push back

len int: 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

added in API level 1
public void unread (char[] cbuf)

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 char: Character array to push back

Throws
IOException If there is insufficient room in the pushback buffer, or if some other I/O error occurs

unread

added in API level 1
public void unread (int c)

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 int: 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