Convert OutputStream to byte array in Java with examples

In this post, I will be sharing how to convert OutputStream to byte array in Java with examples.

1. Convert OutputStream to byte array using toByteArray() method

2. Convert OutputStream to ByteBuffer using the wrap() method

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1. Convert OutputStream to byte array using toByteArray() method

We can easily convert OutputStream to a byte array by following the below steps:

1. Create an object of ByteArrayOutputStream.
2. Write data to ByteArrayOutputStream.
3. Extract byte[] from ByteArrayOutputStream using toByteArray() method as shown below in the example.

Java Program

 import java.io.IOException;
import java.io.ByteArrayOutputStream;

public class OutputStreamToByteArray1 {
    public static void main(String args[]) throws IOException {
        // Given string 
        String string1 = "Alive is Awesome";
        // Creating ByteArrayOutputStream object
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        // Fetch Bytes from String
        byte[] array = string1.getBytes();
        // Writing data to an output stream
        outputStream.write(array);
        // Converting output stream to byte array
        byte[] bytes = outputStream.toByteArray();
        // Printing the byte array
        System.out.println("Output: ");
        for(int i=0; i < bytes.length; i++)
        {
            // Show original characters
            System.out.print((char)bytes[i] + "");
        }    
          
    }
}

Output:
Alive is Awesome

2. Convert OutputStream to ByteBuffer using the wrap() method

We can easily convert OutputStream to ByteBuffer by following the below steps:

1. First, the ByteArrayOutputStream class instance should be created.
2. Write the data to the ByteArrayOutputStream.
3. Extract byte[] from ByteArrayOutputStream using toByteArray() function.
4. Converting byte array to ByteBuffer using ByteBuffer.wrap(byte[]) function as shown below in the example.

Java Program

 import java.io.IOException;
import java.nio.ByteBuffer;
import java.io.ByteArrayOutputStream;

public class OutputStreamToByteBuffer1 {
    public static void main(String args[]) throws IOException {
        // Input string 
        String string1 = "Be in present";
        // Creating ByteArrayOutputStream instance
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        // Fetching Bytes from given input string
        byte[] array = string1.getBytes();
        // write data to output stream
        outputStream.write(array);
        // Converting output stream to byte array
        byte[] bytes = outputStream.toByteArray();
        // Converting byte array to ByteBuffer
        ByteBuffer bufferObject = ByteBuffer.wrap(bytes);
        // Printing the ByteBuffer
        System.out.println(bufferObject);
    }
}

Output:
java.nio.HeapByteBuffer[pos=0 lim=13 cap=13]

That's all for today. Please mention in the comments if you have any questions related to how to convert OutputStream to byte array in Java with examples.