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 SummaryFields declared in class java.io.FilterReaderin
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Constructor SummaryConstructorsConstructorDescriptionPushbackReader(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.
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Method SummaryModifier and TypeMethodDescriptionvoidclose()Closes the stream and releases any system resources associated with it.voidmark(int readAheadLimit) Marks the present position in the stream.booleanTells whether this stream supports the mark() operation, which it does not.intread()Reads a single character.booleanready()Tells whether this stream is ready to be read.voidreset()Resets the stream.voidunread(char[] cbuf) Pushes back an array of characters by copying it to the front of the pushback buffer.voidunread(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.voidunread(int c) Pushes back a single character by copying it to the front of the pushback buffer.Methods declared in class java.io.FilterReaderread, skipMethods declared in class java.io.ReadernullReader, of, read, read, transferTo
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Constructor Details- 
PushbackReaderCreates 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
 
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PushbackReaderCreates 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- 
readReads a single character.- Overrides:
- readin 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
 
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unreadPushes 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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unreadPushes 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 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
 
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unreadPushes 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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readyTells whether this stream is ready to be read.- Overrides:
- readyin 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
 
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markMarks the present position in the stream. Themarkfor classPushbackReaderalways throws an exception.- Overrides:
- markin 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
 
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resetResets the stream. Theresetmethod ofPushbackReaderalways throws an exception.- Overrides:
- resetin class- FilterReader
- Throws:
- IOException- Always, since reset is not supported
 
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markSupportedpublic boolean markSupported()Tells whether this stream supports the mark() operation, which it does not.- Overrides:
- markSupportedin class- FilterReader
- Returns:
- true if and only if this stream supports the mark operation.
 
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closeCloses 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:
- closein interface- AutoCloseable
- Specified by:
- closein interface- Closeable
- Specified by:
- closein class- Reader
- Throws:
- IOException- If an I/O error occurs
 
 
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