Class java.io.BufferedReader - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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Class java.io.BufferedReader

java.lang.Object
   |
   +----java.io.Reader
           |
           +----java.io.BufferedReader

public class BufferedReader
extends Reader

Read text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines.

The buffer size may be specified, or the default size may be used. The default is large enough for most purposes.

In general, each read request made of a Reader causes a corresponding read request to be made of the underlying character or byte stream. It is therefore advisable to wrap a BufferedReader around any Reader whose read() operations may be costly, such as FileReaders and InputStreamReaders. For example,

 BufferedReader in
   = new BufferedReader(new FileReader("foo.in"));

will buffer the input from the specified file. Without buffering, each invocation of read() or readLine() could cause bytes to be read from the file, converted into characters, and then returned, which can be very inefficient.

Programs that use DataInputStreams for textual input can be localized by replacing each DataInputStream with an appropriate BufferedReader.

See Also:: FileReader, InputStreamReader

BufferedReader(Reader): Create a buffering character-input stream that uses a default-sized input buffer.
BufferedReader(Reader, int): Create a buffering character-input stream that uses an input buffer of the specified size.

close(): Close the stream.
mark(int): Mark the present position in the stream.
markSupported(): Tell whether this stream supports the mark() operation, which it does.
read(): Read a single character.
read(char[], int, int): Read characters into a portion of an array.
readLine(): Read a line of text.
ready(): Tell whether this stream is ready to be read.
reset(): Reset the stream to the most recent mark.
skip(long): Skip characters.

BufferedReader

 public BufferedReader(Reader in,
                       int sz)

Create a buffering character-input stream that uses an input buffer of the specified size.

Parameters:: in - A Reader; sz - Input-buffer size
Throws: IllegalArgumentException: If sz is <= 0

BufferedReader

 public BufferedReader(Reader in)

Create a buffering character-input stream that uses a default-sized input buffer.

Parameters:: in - A Reader

read

 public int read() throws IOException

Read a single character.

Throws: IOException: If an I/O error occurs
Overrides:: read in class Reader

read

 public int read(char cbuf[],
                 int off,
                 int len) throws IOException

Read characters into a portion of an array.

Ordinarily this method takes characters from this stream's character buffer, filling it from the underlying stream as necessary. If, however, the buffer is empty, the mark is not valid, and the requested length is at least as large as the buffer, then this method will read characters directly from the underlying stream into the given array. Thus redundant BufferedReaders will not copy data unnecessarily.

Parameters:: cbuf - Destination buffer; off - Offset at which to start storing characters; len - Maximum number of characters to read
Returns:: The number of bytes read, or -1 if the end of the stream has been reached
Throws: IOException: If an I/O error occurs
Overrides:: read in class Reader

readLine

 public String readLine() throws IOException

Read a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.

Returns:: A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached
Throws: IOException: If an I/O error occurs

skip

 public long skip(long n) throws IOException

Skip characters.

Parameters:: n - The number of characters to skip
Returns:: The number of characters actually skipped
Throws: IOException: If an I/O error occurs
Overrides:: skip in class Reader

ready

 public boolean ready() throws IOException

Tell whether this stream is ready to be read. A buffered character stream is ready if the buffer is not empty, or if the underlying character stream is ready.

Throws: IOException: If an I/O error occurs
Overrides:: ready in class Reader

markSupported

 public boolean markSupported()

Tell whether this stream supports the mark() operation, which it does.

Overrides:: markSupported in class Reader

mark

 public void mark(int readAheadLimit) throws IOException

Mark the present position in the stream. Subsequent calls to reset() will attempt to reposition the stream to this point.

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. A limit value larger than the size of the input buffer will cause a new buffer to be allocated whose size is no smaller than limit. Therefore large values should be used with care.
Throws: IllegalArgumentException: If readAheadLimit is < 0
Throws: IOException: If an I/O error occurs
Overrides:: mark in class Reader

reset

 public void reset() throws IOException

Reset the stream to the most recent mark.

Throws: IOException: If the stream has never been marked, or if the mark has been invalidated
Overrides:: reset in class Reader

close

 public void close() throws IOException

Close the stream.

Throws: IOException: If an I/O error occurs
Overrides:: close in class Reader

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