Java ByteArrayOutputStream Class

Java ByteArrayOutputStream class is used to write common data into multiple files. In this stream, the data is written into a byte array which can be written to multiple streams later.

The ByteArrayOutputStream holds a copy of data and forwards it to multiple streams.

The buffer of ByteArrayOutputStream automatically grows according to data.

Java ByteArrayOutputStream class declaration

Let's see the declaration for Java.io.ByteArrayOutputStream class:

Java ByteArrayOutputStream class constructors

Constructor	Description
ByteArrayOutputStream()	Creates a new byte array output stream with the initial capacity of 32 bytes, though its size increases if necessary.
ByteArrayOutputStream(int size)	Creates a new byte array output stream, with a buffer capacity of the specified size, in bytes.

Java ByteArrayOutputStream class methods

Method	Description
int size()	It is used to returns the current size of a buffer.
byte[] toByteArray()	It is used to create a newly allocated byte array.
String toString()	It is used for converting the content into a string decoding bytes using a platform default character set.
String toString(String charsetName)	It is used for converting the content into a string decoding bytes using a specified charsetName.
void write(int b)	It is used for writing the byte specified to the byte array output stream.
void write(byte[] b, int off, int len	It is used for writing len bytes from specified byte array starting from the offset off to the byte array output stream.
void writeTo(OutputStream out)	It is used for writing the complete content of a byte array output stream to the specified output stream.
void reset()	It is used to reset the count field of a byte array output stream to zero value.
void close()	It is used to close the ByteArrayOutputStream.

Example of Java ByteArrayOutputStream

Let's see a simple example of java ByteArrayOutputStream class to write common data into 2 files: f1.txt and f2.txt.

package com.javatpoint;
import java.io.*;
public class DataStreamExample {
public static void main(String args[])throws Exception{  
	  FileOutputStream fout1=new FileOutputStream("D:\\f1.txt");  
	  FileOutputStream fout2=new FileOutputStream("D:\\f2.txt");  
	  
	  ByteArrayOutputStream bout=new ByteArrayOutputStream();  
	  bout.write(65);  
	  bout.writeTo(fout1);  
	  bout.writeTo(fout2);  
	  
	  bout.flush();  
	  bout.close();//has no effect  
	  System.out.println("Success...");  
	 }  
	} 

Output: