code: public static String verifyReadFile(File file){
  		if (file == null){
  			return "The file is null.";
  		}
  
  		String absolutePath=file.getAbsolutePath();
  		if (!file.exists()){
  			return "The path '"+absolutePath+"' do not exits.";
  		}
  
  		if (!file.isFile()){
  			return "The path '"+absolutePath+"' is not a file.";
  		}
  		
  		if (!file.canRead()){
  			return "We have not permision to read the path:'"+absolutePath+"'.";
  		}
  
  		return null;				
  	}
docs: Verificamos que file es un fichero y que tenemos permisos de lectura
  @param dir
  @return