Class PushbackReader
java.lang.Object
java.io.Reader
java.io.FilterReader
java.io.PushbackReader
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Readable
A character-stream reader that allows characters to be pushed back into the
stream.
- Since:
- 1.1
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Field Summary
Fields declared in class java.io.FilterReader
in
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Constructor Summary
ConstructorDescriptionPushbackReader
(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 TypeMethodDescriptionvoid
close()
Closes the stream and releases any system resources associated with it.void
mark
(int readAheadLimit) Marks the present position in the stream.boolean
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 java.io.FilterReader
read, skip
Methods declared in class java.io.Reader
nullReader, read, read, transferTo
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Constructor Details
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PushbackReader
Creates a new pushback reader with a pushback buffer of the given size.- Parameters:
in
- The reader from which characters will be readsize
- The size of the pushback buffer- Throws:
IllegalArgumentException
- ifsize <= 0
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PushbackReader
Creates a new pushback reader with a one-character pushback buffer.- Parameters:
in
- The reader from which characters will be read
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Method Details
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read
Reads a single character.- Overrides:
read
in classFilterReader
- Returns:
- The character read, or -1 if the end of the stream has been reached
- Throws:
IOException
- If an I/O error occurs
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unread
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
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unread
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 valuecbuf[off]
, the character after that will have the valuecbuf[off+1]
, and so forth.- Parameters:
cbuf
- Character arrayoff
- Offset of first character to push backlen
- 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
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unread
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 valuecbuf[0]
, the character after that will have the valuecbuf[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
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ready
Tells whether this stream is ready to be read.- Overrides:
ready
in classFilterReader
- 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
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mark
Marks the present position in the stream. Themark
for classPushbackReader
always throws an exception.- Overrides:
mark
in classFilterReader
- 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
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reset
Resets the stream. Thereset
method ofPushbackReader
always throws an exception.- Overrides:
reset
in classFilterReader
- Throws:
IOException
- Always, since reset is not supported
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markSupported
public boolean markSupported()Tells whether this stream supports the mark() operation, which it does not.- Overrides:
markSupported
in classFilterReader
- Returns:
- true if and only if this stream supports the mark operation.
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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. This method will block while there is another thread blocking on the reader.- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
- Specified by:
close
in classReader
- Throws:
IOException
- If an I/O error occurs
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