Работа с файлами.

Пишем и читаем byte[].

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

public class ReadWriteFile {
 
 public byte[] readFile(File file) {
  try {
   InputStream is = new FileInputStream(file);   
   byte[] bytes = decodeBase64(is);   
         is.close();
   return bytes;
  } catch (FileNotFoundException e) {
   e.printStackTrace(); 
   return null;
  } catch (IOException e) {
   e.printStackTrace();
   return null;
  }
 }
 
 public void writeFile(String fileName, byte[] fileByteArray) {
  FileOutputStream fos;
  try {
   fos = new FileOutputStream(fileName);
   fos.write(fileByteArray);
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }  
}