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java.io
Class PushbackReader
java.lang.Object
java.io.Reader
java.io.FilterReader
java.io.PushbackReader
-
All Implemented Interfaces:
-
Closeable
,
Readable
-
public class PushbackReader
- extends FilterReader
A character-stream reader that allows characters to be pushed back into the stream.
-
Since:
-
JDK1.1
Constructor Summary
|
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
|
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)
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.
character.
|
Methods inherited from class java.lang.
Object
|
clone
,
equals
,
finalize
,
getClass
,
hashCode
,
notify
,
notifyAll
,
toString
,
wait
,
wait
,
wait
|
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 is <= 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
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
read
public int read(char[] cbuf,
int off,
int len)
throws IOException
-
Reads 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
-
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.
Pushes back a single character.
-
-
Parameters:
-
c - The
int value representing a
character to
be pushed
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
-
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.
-
-
Specified by:
-
close
in interface
Closeable
-
Overrides:
-
close
in class
FilterReader
-
-
Throws:
-
IOException
- If an I/O error occurs
skip
public long skip(long n)
throws IOException
-
Skips 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