Convert file to byte array and vice versa

Otherwise Try this :

Converting File To Bytes

  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;


   public class Temp {

        public static void main(String[] args) {

         File file = new File("c:/EventItemBroker.java");

         byte[] b = new byte[(int) file.length()];
         try {
               FileInputStream fileInputStream = new FileInputStream(file);
               fileInputStream.read(b);
               for (int i = 0; i < b.length; i++) {
                           System.out.print((char)b[i]);
                }
          } catch (FileNotFoundException e) {
                      System.out.println("File Not Found.");
                      e.printStackTrace();
          }
          catch (IOException e1) {
                   System.out.println("Error Reading The File.");
                    e1.printStackTrace();
          }

       }
    }

Converting Bytes to File

      public class WriteByteArrayToFile {

         public static void main(String[] args) {

            String strFilePath = "Your path";
            try {
                 FileOutputStream fos = new FileOutputStream(strFilePath);
                 String strContent = "Write File using Java ";

                 fos.write(strContent.getBytes());
                 fos.close();
           }
          catch(FileNotFoundException ex)   {
                 System.out.println("FileNotFoundException : " + ex);
          }
         catch(IOException ioe)  {
                 System.out.println("IOException : " + ioe);
          }

       }
     }

I think you misunderstood what the java.io.File class really represents. It is just a representation of the file on your system, i.e. its name, its path etc.

Did you even look at the Javadoc for the java.io.File class? Have a look here If you check the fields it has or the methods or constructor arguments, you immediately get the hint that all it is, is a representation of the URL/path.

Oracle provides quite an extensive tutorial in their Java File I/O tutorial, with the latest NIO.2 functionality too.

With NIO.2 you can read it in one line using java.nio.file.Files.readAllBytes().

Similarly you can use java.nio.file.Files.write() to write all bytes in your byte array.

UPDATE

Since the question is tagged Android, the more conventional way is to wrap the FileInputStream in a BufferedInputStream and then wrap that in a ByteArrayInputStream. That will allow you to read the contents in a byte[]. Similarly the counterparts to them exist for the OutputStream.

You can't do this. A File is just an abstract way to refer to a file in the file system. It doesn't contain any of the file contents itself.

If you're trying to create an in-memory file that can be referred to using a File object, you aren't going to be able to do that, either, as explained in this thread, this thread, and many other places..