java.io
Class 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.
Version:
1.22, 00/02/02
Author:
Mark Reinhold
Since:
JDK1.1
See Also:
PrintWriter
FileWriter
OutputStreamWriter
Field Detail

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()
Check to make sure that the stream has not been closed

flushBuffer

void flushBuffer()
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.

write

public void write(int c)
Write a single character.
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)
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.

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)
Write a portion of a String.
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()
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()
Flush the stream.
Throws:
IOException - If an I/O error occurs

close

public void close()
Close the stream.
Throws:
IOException - If an I/O error occurs