BufferedWriter

AI-generated Key Takeaways

• BufferedWriter efficiently writes text by buffering characters, arrays, and strings to a character-output stream.

• It uses the system's line separator for newLine(), ensuring platform compatibility.

• Wrapping BufferedWriter around costly Writers like FileWriter improves performance by reducing frequent write operations.

• It offers methods to write single characters, parts of strings, and character arrays.

• BufferedWriter can be initialized with a custom buffer size or a default size suitable for most cases.

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.

See Also

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

Inherited Field Summary

From class java.io.Writer

protected Object

lock

The object used to synchronize operations on this stream.

Public Constructor Summary

	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.

Public Method Summary

void	close() Closes the stream, flushing it first.
void	flush() Flushes the stream.
void	newLine() Writes a line separator.
void	write(int c) Writes a single character.
void	write(String s, int off, int len) Writes a portion of a String.
void	write(char[] cbuf, int off, int len) Writes a portion of an array of characters.

Inherited Method Summary

From class java.io.Writer

Writer	append(char c) Appends the specified character to this writer.
Writer	append(CharSequence csq, int start, int end) Appends a subsequence of the specified character sequence to this writer.
Writer	append(CharSequence csq) Appends the specified character sequence to this writer.
abstract void	close() Closes the stream, flushing it first.
abstract void	flush() Flushes the stream.
void	write(String str) Writes a string.
void	write(int c) Writes a single character.
void	write(String str, int off, int len) Writes a portion of a string.
abstract void	write(char[] cbuf, int off, int len) Writes a portion of an array of characters.
void	write(char[] cbuf) Writes an array of characters.

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.lang.Appendable

abstract Appendable	append(char c) Appends the specified character to this Appendable.
abstract Appendable	append(CharSequence csq, int start, int end) Appends a subsequence of the specified character sequence to this Appendable.
abstract Appendable	append(CharSequence csq) Appends the specified character sequence to this Appendable.

From interface java.io.Closeable

abstract void

close() Closes this stream and releases any system resources associated with it.

From interface java.io.Flushable

abstract void

flush() Flushes this stream by writing any buffered output to the underlying stream.

From interface java.lang.AutoCloseable

abstract void

close() Closes this resource, relinquishing any underlying resources.

Public Constructors

public BufferedWriter (Writer out)

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

Parameters

out	A Writer

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

Public Methods

public void close ()

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.

Throws

IOException

public void flush ()

Flushes the stream.

Throws

IOException	If an I/O error occurs

public void newLine ()

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

public void write (int c)

Writes a single character.

Parameters

c	int specifying a character to be written

Throws

IOException	If an I/O error occurs

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

Writes a portion of a String.

If the value of the len parameter is negative then no characters are written. This is contrary to the specification of this method in the {@linkplain java.io.Writer#write(java.lang.String,int,int) superclass}, which requires that an IndexOutOfBoundsException be thrown.

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

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

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.

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