java.io
Class BufferedWriter

java.lang.Object
  extended byjava.io.Writer
      extended byjava.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