Create DataOutputStream from FileOutputStream : FileOutputStream « File « Java Tutorial

1. Java Tutorial
2. File
3. FileOutputStream

import java.io.DataOutputStream;
import java.io.FileOutputStream;

public class Main {

  public static void main(String[] args) throws Exception {
    FileOutputStream fos = new FileOutputStream("C:/demo.txt");

    DataOutputStream dos = new DataOutputStream(fos);
  }
}