- java.lang.Object
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- java.io.Reader
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- java.io.FilterReader
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- java.io.PushbackReader
 
 
 
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- All Implemented Interfaces:
- Closeable,- AutoCloseable,- Readable
 
 public class PushbackReader extends FilterReader 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.FilterReaderin
 
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Constructor SummaryConstructors Constructor Description 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.
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Method SummaryAll Methods Instance Methods Concrete Methods Modifier and Type Method Description voidclose()Closes the stream and releases any system resources associated with it.voidmark(int readAheadLimit)Marks the present position in the stream.booleanmarkSupported()Tells whether this stream supports the mark() operation, which it does not.intread()Reads a single character.intread(char[] cbuf, int off, int len)Reads characters into a portion of an array.booleanready()Tells whether this stream is ready to be read.voidreset()Resets the stream.longskip(long n)Skips characters.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.ReadernullReader, read, read, transferTo
 
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Constructor Detail- 
PushbackReaderpublic 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 <= 0
 
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PushbackReaderpublic PushbackReader(Reader in) 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 Detail- 
readpublic int read() throws IOExceptionReads 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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readpublic int read(char[] cbuf, int off, int len) throws IOExceptionReads characters into a portion of an array.- Overrides:
- readin 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
- IndexOutOfBoundsException- If an I/O error occurs
 
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unreadpublic void unread(int c) throws IOExceptionPushes 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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unreadpublic void unread(char[] cbuf, int off, int len) throws IOExceptionPushes 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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unreadpublic void unread(char[] cbuf) throws IOExceptionPushes 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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readypublic boolean ready() throws IOExceptionTells 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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markpublic void mark(int readAheadLimit) throws IOExceptionMarks 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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resetpublic void reset() throws IOExceptionResets 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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closepublic void close() throws IOExceptionCloses 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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skippublic long skip(long n) throws IOExceptionSkips characters. This method will block until some characters are available, an I/O error occurs, or the end of the stream is reached.- Overrides:
- skipin class- FilterReader
- Parameters:
- n- The number of characters to skip
- Returns:
- The number of characters actually skipped
- Throws:
- IllegalArgumentException- If- nis negative.
- IOException- If an I/O error occurs
 
 
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