Class BufferedWriter

java.lang.Object

java.io.Writer

java.io.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.

API Note:

Once wrapped in a BufferedWriter, the underlying Writer should not be used directly nor wrapped with another writer.

Since:

1.1

See Also:

• PrintWriter
• FileWriter
• OutputStreamWriter
• Files.newBufferedWriter(Path, Charset, OpenOption...)

Field Summary

Fields declared in class Writer

lock

Modifier and Type	Field	Description
protected Object	lock	The object used to synchronize operations on this stream.

Constructor Summary

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.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes the stream, flushing it first.
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 Writer

append, append, append, nullWriter, write, write

Modifier and Type	Method	Description
Writer	append(char c)	Appends the specified character to this writer.
Writer	append(CharSequence csq)	Appends the specified character sequence to this writer.
Writer	append(CharSequence csq, int start, int end)	Appends a subsequence of the specified character sequence to this writer.
static Writer	nullWriter()	Returns a new Writer which discards all characters.
void	write(char[] cbuf)	Writes an array of characters.
void	write(String str)	Writes a string.

Methods declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Constructor Details

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

Method Details

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

close

public void close()
           throws IOException

Description copied from class: Writer

Closes the stream, flushing it first. Once the stream has been closed, further write() or flush() invocations will cause an IOException to be thrown. Closing a previously closed stream has no effect.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in class Writer

Throws:

IOException - If an I/O error occurs