PushbackReader (Java Platform SE 6) - JDK 5 Documentation v6.0, Java 2 SDK 英文文档

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Java™ Platform
Standard Ed. 6

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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
extends FilterReader

A character-stream reader that allows characters to be pushed back into the stream.

Since:: JDK1.1

Field Summary

Fields inherited from class java.io.FilterReader

in

Fields inherited from class java.io.Reader

lock

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.

Methods inherited from class java.io.Reader

read, read

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Fields inherited from class java.io.FilterReader
`in`

Fields inherited from class java.io.Reader
`lock`

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.

Methods inherited from class java.io.Reader
`read, read`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

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

Method Detail

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.

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

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

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For further API reference and developer documentation, see Java SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

PushbackReader (Java Platform SE 6) - JDK 5 Documentation v6.0, Java 2 SDK 英文文档

java.io Class PushbackReader

PushbackReader

PushbackReader

read

read

unread

unread

unread

ready

mark

reset

markSupported

close

skip

java.io
Class PushbackReader