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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)
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.lang.
Object
|
clone
,
equals
,
finalize
,
getClass
,
hashCode
,
notify
,
notifyAll
,
toString
,
wait
,
wait
,
wait
|
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
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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
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
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off - Offset at which to start writing characters
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len - Maximum number of characters to read
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Returns:
-
The number of characters read, or -1 if the end of the stream has been reached
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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.
-
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Parameters:
-
cbuf - Character array
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off - Offset of first character to push back
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len - Number of characters to push back
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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.
-
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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.
-
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Overrides:
-
ready
in class
FilterReader
-
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Returns:
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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.
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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
-
-
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.
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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.
-
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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.
-
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Overrides:
-
markSupported
in class
FilterReader
-
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Returns:
-
true if and only if this stream supports the mark operation.
close
public void close()
throws IOException
-
Close the stream.
-
-
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
-
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
-
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Parameters:
-
n - The number of characters to skip
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Returns:
-
The number of characters actually skipped
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Throws:
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IllegalArgumentException
- If n is negative.
-
IOException
- If an I/O error occurs