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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.

Since:

JDK1.1

Version:

1.16, 98/04/30

See Also:

FileReader, InputStreamReader

Field Summary

char[]	cb
static int	defaultCharBufferSize
static int	defaultExpectedLineLength
Reader	in
static int	INVALIDATED
int	markedChar
int	nChars
int	nextChar
int	readAheadLimit
static int	UNMARKED

Fields inherited from class java.io.Reader

lock, maxSkipBufferSize, skipBuffer

Constructor Summary

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

BufferedReader(Reader in)
Create a buffering character-input stream that uses a default-sized input buffer.

Method Summary

void	close() Close the stream.
void	ensureOpen() Check to make sure that the stream has not been closed
void	fill() Fill the input buffer, taking the mark into account if it is valid.
void	mark(int readAheadLimit) Mark the present position in the stream.
boolean	markSupported() Tell whether this stream supports the mark() operation, which it does.
int	read() Read a single character.
int	read(char[] cbuf, int off, int len) Read characters into a portion of an array.
java.lang.String	readLine(boolean skipLF) Read a line of text.
java.lang.String	readLine() Read a line of text.
boolean	ready() Tell whether this stream is ready to be read.
void	reset() Reset the stream to the most recent mark.
long	skip(long n) Skip characters.

Methods inherited from class java.io.Reader

close, mark, markSupported, read, read, read, ready, reset, skip

Methods inherited from class java.lang.Object

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

Field Detail

in

private Reader in

cb

private char[] cb

nChars

private int nChars

nextChar

private int nextChar

INVALIDATED

private static final int INVALIDATED

UNMARKED

private static final int UNMARKED

markedChar

private int markedChar

readAheadLimit

private int readAheadLimit

defaultCharBufferSize

private static int defaultCharBufferSize

defaultExpectedLineLength

private static int defaultExpectedLineLength

Constructor Detail

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:

java.lang.IllegalArgumentException - If sz is <= 0="0" <="<" />l>

BufferedReader

public BufferedReader(Reader in)

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

Parameters:

in - A Reader

Method Detail

ensureOpen

private void ensureOpen()
                throws IOException

Check to make sure that the stream has not been closed

fill

private void fill()
          throws IOException

Fill the input buffer, taking the mark into account if it is valid.

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

java.lang.String readLine(boolean skipLF)
                   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.

Parameters:

skipLF - If true, the next '\n' will be skipped

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

See Also:

java.io.LineNumberReader#readLine()

readLine

public java.lang.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:

java.lang.IllegalArgumentException - If readAheadLimit is < 0 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