I apologize, but there is no such class as "DataOutputAsStream" in the Apache Commons IO library. It seems that you might be confusing it with other class or package. Apache Commons IO focuses on providing utility classes for file and I/O operations, and it doesn't have a class specifically for converting a DataOutput object to a Stream.

Java provides the DataOutputStream class which is a subclass of OutputStream and provides methods to write data types like int, long, float and double, etc. You can use this class to write to an output stream, and then use the ByteArrayOutputStream class to convert it to a byte array.

Here is an example of using DataOutputStream to write an integer value to a ByteArrayOutputStream:

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

public class DataOutputAsStreamExample {
    public static void main(String[] args) throws IOException {
        ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
        DataOutputStream dataOut = new DataOutputStream(byteOut);
        dataOut.writeInt(123);
        dataOut.flush();
        byte[] byteArray = byteOut.toByteArray();
    }
}

In this example, we create an instance of ByteArrayOutputStream and wrap it with a DataOutputStream. Then we use the writeInt() method to write an integer value to the DataOutputStream. We flush the stream and convert it to a byte array using the toByteArray() method.