BufferedOutputStream

File Input/Output operations consume a lot of important resources and are time consuming. Hence, writing a chunk of bytes to a file is faster than writing one byte at a time. It speeds up the I/O process.

BufferedOutputStream class is used to create such buffered output stream using which a chunk of bytes stored in the local buffer of BufferedOutputStream, is written out to a file.

Constructors :

BufferedOutputStream(OutputStream os)
This constructor creates a BufferedOutputStream object to write a chunk of byte to a file, which is accessed by an OutputStream. Example-: `File file= new File("D:/Textbook.txt"); FileOutputStream fos= new FileOutputStream(file); BufferedOutputStream fis= new BufferedOutputStream(fos);`

This example has created a BufferedOutputStream object to write the bytes stored in its local buffer to a file D:/Textbook.txt through OutputStream i.e. FileOutputStream, passed to constructor.

Point to remember

FileOutputStream is a subclass of OutputStream

Methods for writing using BufferedOutputStream

Some methods that we generally use while working with BufferedOutputStream are shown in the table below :

Methods	Description
flush()	This method flushes any buffered data to be written out of this output stream.
write(int b)	This method writes one byte at a time to this output stream.
write(byte[])	This method writes a whole byte array at a time to this output stream.
close()	This method closes this outut stream and also frees any resources connected with this output stream.

Program to write to a file using BufferedOutputStream.

In this code, we are creating a BufferedOutputStream object to write the bytes stored in its local buffer to a file D:/Textbook.txt through OutputStream i.e. FileOutputStream.

//Program to create a BufferedIOutputStream to write(one byte at a time) out to an existing file.

import java.io.*;
class A
{
public static void main(String... ar)
{

String str="Java is the best programming language";
byte b[]=str.getBytes();

try
{
FileOutputStream fos= new FileOutputStream("D://TextBook.txt");
BufferedOutputStream bos= new BufferedOutputStream(fos); ///A local buffer is created which is big-
							//enough to hold a chunk of bytes to be
							//written out to a file TextBook.txt
							
bos.write(b); //writes to local buffer
bos.flush();
bos.close();
fos.close();
}
catch(IOException e)
{
System.out.println(e);
}

}
}

Output is -:

A file called "TextBook.txt" is created in D: drive, with the contents -:
Java is the best programming language

Program Analysis

Calling the constructor of BufferedOutputStream creates a local buffer, big enough to hold a chunk of bytes to be written out to a file.
Data is written (one byte at a time) to the buffer of BufferOutputStream by write(int b) method.
A chunk of bytes in buffer is written to the file at once by flush() method or close() method.
Finally, the opened input streams are closed by close() method to free any connected resources.

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