code: public static OutputStream toFile(String filepath) throws FileNotFoundException {
  		if(Strings.isValid(filepath)) {
  			return new FileOutputStream(new File(filepath));
  		}
  		return null;
  	}
docs: Returns an output stream corresponding to the given file.
  
  @param file
  a string representing the output file path.
  @return
  a {@code FileOutputStrea} to the given file, or {@code null} if the file
  is not valid.
  @throws FileNotFoundException