How to convert an input stream to byte array in java?

The InputStream class in Java provides read() method. This method accepts a byte array and it reads the contents of the input stream to the given byte array.

To convert an InputStream to a byte array, We can use the ByteArrayOutputStream class to read data from the InputStream and write it into a byte array.

Methods to Convert InputStream to Byte Array

Let's compare the methods to convert InputStream to Byte Array in the below table ?

To convert an input stream to byte array in Java is quite easy. Let us learn the following methods:

Converting InputStream to Byte Array

This method demonstrates how to read data from the InputStream and convert it into a byte array, then print the contents of the byte stream as a string using a BufferedInputStream.

Example

The program reads data from the standard input using a BufferedInputStream and stores it in a byte array of size 1024. Then it converts the byte array to a string.

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
public class StreamToByteArray {
   public static void main(String args[]) throws IOException{    
      InputStream is = new BufferedInputStream(System.in);
      byte [] byteArray = new byte[1024];
      System.out.println("Enter some data");
      is.read(byteArray);      
      String s = new String(byteArray);
      System.out.println("Contents of the byte stream are :: "+ s);
   }  
}

Output

Following is the output of the above program ?

Enter some data
hello how are you
Contents of the byte stream are :: hello how are you

Alternative Solution Using Apache Commons IOUtils

Apache Commons provides a library named org.apache.commons.io and, the following is the maven dependency to add the library to your project.

<dependency>
    <groupId>commons-io</groupId>
   <artifactId>commons-io</artifactId>
   <version>2.5</version>
</dependency>

This package provides a class known as IOUtils. the toByteArray () method of this class accepts an InputStream object and returns the contents in the stream in the form of a byte array:

Example

Following is another example that reads the contents of a file named "data" into a byte array using FileInputStream and the Apache Commons IO IOUtils.toByteArray() method. It converts the byte array to a string.

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import org.apache.commons.io.IOUtils;
public class StreamToByteArray2IOUtils {
   public static void main(String args[]) throws IOException{    
      File file = new File("data");
      FileInputStream fis = new FileInputStream(file);
      byte [] byteArray = IOUtils.toByteArray(fis);
      String s = new String(byteArray);
      System.out.println("Contents of the byte stream are :: "+ s);
   }  
}

Output

The above program produce the following result ?

Contents of the byte stream are :: hello how are you

Converting InputStream to Byte Array Using OutputStream

The following method is used to read data from an InputStream, converting it into a byte array using OutputStream.

Example

In this program, we convert an 'InputStream' to a byte array using 'ByteArrayOutputStream'. It reads data from the input stream, writes it to the output stream, and then converts the accumulated data into a byte array as a string.

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

public class InputStreamToByteArray {
   public static byte[] convertInputStreamToByteArray(InputStream inputStream) throws IOException {
      ByteArrayOutputStream buffer = new ByteArrayOutputStream();
      int bytesRead;
      byte[] data = new byte[1024];
   
      while ((bytesRead = inputStream.read(data, 0, data.length)) != -1) {
         buffer.write(data, 0, bytesRead);
      }
   
      buffer.flush();
      return buffer.toByteArray();
   }
   
   public static void main(String[] args) {
      String exampleInput = "Hello, World!";
      InputStream inputStream = new ByteArrayInputStream(exampleInput.getBytes());
   
      try {
         byte[] byteArray = convertInputStreamToByteArray(inputStream);
   
         System.out.println("Contents of the byte stream are :: " + new String(byteArray));
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output

The above program produce the following result ?

Contents of the byte stream are :: Hello, World!