java.io
Class BufferedWriter

java.lang.Object
  java.io.Writer
      java.io.BufferedWriter

public class BufferedWriter

extends Writer

Write text to a character-output stream, buffering characters so as to provide for the efficient writing of single characters, arrays, and strings.

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

A newLine() method is provided, which uses the platform's own notion of line separator as defined by the system property line.separator. Not all platforms use the newline character ('\n') to terminate lines. Calling this method to terminate each output line is therefore preferred to writing a newline character directly.

In general, a Writer sends its output immediately to the underlying character or byte stream. Unless prompt output is required, it is advisable to wrap a BufferedWriter around any Writer whose write() operations may be costly, such as FileWriters and OutputStreamWriters. For example,

 PrintWriter out
   = new PrintWriter(new BufferedWriter(new FileWriter("foo.out")));
 

will buffer the PrintWriter's output to the file. Without buffering, each invocation of a print() method would cause characters to be converted into bytes that would then be written immediately to the file, which can be very inefficient.

Since:

JDK1.1

Author:

Mark Reinhold

See Also:

PrintWriter, FileWriter, OutputStreamWriter

Field Summary

private char[]	cb
private static int	defaultCharBufferSize
private String	lineSeparator Line separator string.
private int	nChars
private int	nextChar
private Writer	out

Fields inherited from class java.io.Writer

lock

Constructor Summary

BufferedWriter(Writer out)
Create a buffered character-output stream that uses a default-sized output buffer.

BufferedWriter(Writer out, int sz)
Create a new buffered character-output stream that uses an output buffer of the given size.

Method Summary

void	close() Close the stream.
private void	ensureOpen() Check to make sure that the stream has not been closed
void	flush() Flush the stream.
(package private) void	flushBuffer() Flush the output buffer to the underlying character stream, without flushing the stream itself.
private int	min(int a, int b) Our own little min method, to avoid loading java.lang.Math if we've run out of file descriptors and we're trying to print a stack trace.
void	newLine() Write a line separator.
void	write(char[] cbuf, int off, int len) Write a portion of an array of characters.
void	write(int c) Write a single character.
void	write(String s, int off, int len) Write a portion of a String.

Methods inherited from class java.io.Writer

write, write

Methods inherited from class java.lang.Object

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

Field Detail

out

private Writer out

cb

private char[] cb

nChars

private int nChars

nextChar

private int nextChar

defaultCharBufferSize

private static int defaultCharBufferSize

lineSeparator

private String lineSeparator

Line separator string. This is the value of the line.separator property at the moment that the stream was created.

Constructor Detail

BufferedWriter

public BufferedWriter(Writer out)

Create a buffered character-output stream that uses a default-sized output buffer.

Parameters:

out - A Writer

BufferedWriter

public BufferedWriter(Writer out,
                      int sz)

Create a new buffered character-output stream that uses an output buffer of the given size.

Parameters:

out - A Writer

sz - Output-buffer size, a positive integer

Throws:

IllegalArgumentException - If sz is <= 0

Method Detail

ensureOpen

private void ensureOpen()
                 throws IOException

Check to make sure that the stream has not been closed

Throws:

IOException

flushBuffer

void flushBuffer()
           throws IOException

Flush the output buffer to the underlying character stream, without flushing the stream itself. This method is non-private only so that it may be invoked by PrintStream.

Throws:

IOException

write

public void write(int c)
           throws IOException

Write a single character.

Overrides:

write in class Writer

Parameters:

c - int specifying a character to be written.

Throws:

IOException - If an I/O error occurs

min

private int min(int a,
                int b)

Our own little min method, to avoid loading java.lang.Math if we've run out of file descriptors and we're trying to print a stack trace.

write

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

Write a portion of an array of characters.

Ordinarily this method stores characters from the given array into this stream's buffer, flushing the buffer to the underlying stream as needed. If the requested length is at least as large as the buffer, however, then this method will flush the buffer and write the characters directly to the underlying stream. Thus redundant BufferedWriters will not copy data unnecessarily.

Specified by:

write in class Writer

Parameters:

cbuf - A character array

off - Offset from which to start reading characters

len - Number of characters to write

Throws:

IOException - If an I/O error occurs

write

public void write(String s,
                  int off,
                  int len)
           throws IOException

Write a portion of a String.

Overrides:

write in class Writer

Parameters:

s - String to be written

off - Offset from which to start reading characters

len - Number of characters to be written

Throws:

IOException - If an I/O error occurs

newLine

public void newLine()
             throws IOException

Write a line separator. The line separator string is defined by the system property line.separator, and is not necessarily a single newline ('\n') character.

Throws:

IOException - If an I/O error occurs

flush

public void flush()
           throws IOException

Flush the stream.

Specified by:

flush in class Writer

Throws:

IOException - If an I/O error occurs

close

public void close()
           throws IOException

Close the stream.

Specified by:

close in class Writer

Throws:

IOException - If an I/O error occurs