Class BufferedWriter

All Implemented Interfaces:
Closeable, Flushable, Appendable, AutoCloseable 
public class BufferedWriter
extends Writer

Writes 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:
1.1
See Also:
PrintWriter, FileWriter, OutputStreamWriter, Files.newBufferedWriter(java.nio.file.Path, java.nio.charset.Charset, java.nio.file.OpenOption...)

Fields

Fields declared in class java.io.Writer

lock

Constructors

Constructor Description
BufferedWriter​(Writer out)

Creates a buffered character-output stream that uses a default-sized output buffer.
BufferedWriter​(Writer out, int sz)

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

Methods

Modifier and Type Method Description
void flush()

Flushes the stream.
void newLine()

Writes a line separator.
void write​(char[] cbuf, int off, int len)

Writes a portion of an array of characters.
void write​(int c)

Writes a single character.
void write​(String s, int off, int len)

Writes a portion of a String.

Methods declared in class java.io.Writer

append, append, append, close, nullWriter, write, write

Methods declared in class java.lang.Object

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

Constructors

BufferedWriter

public BufferedWriter(Writer out)

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

Parameters:
out - A Writer

BufferedWriter

public BufferedWriter(Writer out,
                      int sz)

Creates 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 <= 0

Methods

write

public void write(int c)
           throws IOException

Writes 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

write

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

Writes 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:
IndexOutOfBoundsException - If off is negative, or len is negative, or off + len is negative or greater than the length of the given array
IOException - If an I/O error occurs

write

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

Writes a portion of a String.

Overrides:
write in class Writer
Implementation Requirements:
While the specification of this method in the superclass recommends that an IndexOutOfBoundsException be thrown if len is negative or off + len is negative, the implementation in this class does not throw such an exception in these cases but instead simply writes no characters.
Parameters:
s - String to be written
off - Offset from which to start reading characters
len - Number of characters to be written
Throws:
IndexOutOfBoundsException - If off is negative, or off + len is greater than the length of the given string
IOException - If an I/O error occurs

newLine

public void newLine()
             throws IOException

Writes 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

Flushes the stream.

Specified by:
flush in interface Flushable
Specified by:
flush in class Writer
Throws:
IOException - If an I/O error occurs

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
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https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/BufferedWriter.html