Java - BufferedOutputStream Class

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Introduction

The Java BufferedOutputStream class implements a buffered output stream. By setting up such an output stream, an application can write bytes to the underlying output stream without necessarily causing a call to the underlying system for each byte written.

Class declaration

Following is the declaration for Java.io.BufferedOutputStream class −

 public class BufferedOutputStream extends FilterOutputStream 

Field

Following are the fields for Java.io.BufferedOutputStream class −

• protected byte[] buf − This is the internal buffer where data is stored.

• protected int count − This is the number of valid bytes in the buffer.

• protected OutputStream out − This is the underlying output stream to be filtered.

Class constructors

Class methods

Methods inherited

This class inherits methods from the following classes −

• Java.io.FilterOutputStream
• Java.io.Object

Here are the examples of how to use the BufferedOutputStream class in Java, each demonstrating a different aspect of its functionality−

Example - Writing Text to a File Using BufferedOutputStream

This example demonstrates how to write a string to a file using BufferedOutputStream.

 package com.tutorialspoint; import java.io.BufferedOutputStream; import java.io.FileOutputStream; import java.io.IOException; public class BufferedOutputStreamDemo { public static void main (String[] args) { String text = "Hello, BufferedOutputStream!"; // Create BufferedOutputStream and FileOutputStream to write content to a file try (FileOutputStream fos = new FileOutputStream("example.txt"); BufferedOutputStream bos = new BufferedOutputStream(fos)) { // write contents to the BufferedOutputStream bos.write(text.getBytes()); // Ensures all data is written to the file bos.flush(); System.out.println("Data written successfully!"); } catch (IOException e) { e.printStackTrace(); } } } 

Output

 Data written successfully! 

After running the program, you can check the content of example.txt in the current directory.

 Hello, BufferedOutputStream! 

Explanation

• This program reads a file example.txt using a BufferedInputStream wrapped around a FileInputStream.

• It reads one byte at a time and prints it as a character.

• The buffer improves efficiency by reducing the number of I/O operations.

Example - Writing Bytes in Chunks Using a Buffer

This example shows how to write an array of bytes in chunks to a file.

 package com.tutorialspoint; import java.io.BufferedOutputStream; import java.io.FileOutputStream; import java.io.IOException; public class BufferedOutputStreamDemo { public static void main(String[] args) { byte[] data = "This is an example of chunked writing.".getBytes(); // Create BufferedOutputStream and FileOutputStream to write content to a file try (FileOutputStream fos = new FileOutputStream("example.txt"); BufferedOutputStream bos = new BufferedOutputStream(fos)) { // define a chunk size int chunkSize = 10; for (int i = 0; i < data.length; i += chunkSize) { // write content as per the chunk size int length = Math.min(chunkSize, data.length - i); bos.write(data, i, length); } // Ensures all data is written to the file bos.flush(); System.out.println("Chunked data written successfully!"); } catch (IOException e) { e.printStackTrace(); } } } 

Output

 Chunked data written successfully! 

After running the program, you can check the content of example.txt in the current directory.

 This is an example of chunked writing. 

Explanation

• The data is split into chunks of 10 bytes and written iteratively.

• The write method with offset and length parameters ensures that only a subset of the array is written during each iteration.

Example - Copying a File Using BufferedInputStream and BufferedOutputStream

We've used a "example.txt" file with following content−

 Welcome to tutorialspoint.com 

This example demonstrates copying the contents of one file to another.

 package com.tutorialspoint; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; public class BufferedOutputStreamDemo { public static void main(String[] args) { // Create BufferedInputStream and FileInputStream to read content from a file // Create BufferedOutputStream and FileOutputStream to write content to a file try (FileInputStream fis = new FileInputStream("example.txt"); BufferedInputStream bis = new BufferedInputStream(fis); FileOutputStream fos = new FileOutputStream("destination.txt"); BufferedOutputStream bos = new BufferedOutputStream(fos)) { // Buffer of 1 KB byte[] buffer = new byte[1024]; int bytesRead; // read till last byte while ((bytesRead = bis.read(buffer)) != -1) { bos.write(buffer, 0, bytesRead); } // Ensures all data is written to the file bos.flush(); System.out.println("File copied successfully!"); } catch (IOException e) { e.printStackTrace(); } } } 

Output

 File copied successfully! 

After running the program, you can check the content of example.txt in the current directory.

 Welcome to tutorialspoint.com 

Explanation

• BufferedInputStream reads data from source.txt in chunks of 1024 bytes.

• BufferedOutputStream writes the data to destination.txt.

• The loop ensures all data from the source file is read and written.