How correctly write to file Runtime process?

Hello, I have such Process request

try {
			Process process = Runtime.getRuntime().exec("ping delfi.lt");
			prinResults(process);
		} catch (Exception e) {
			e.printStackTrace();
		}

in the printResults(process) I'm trying to write process to the file but without any success, the result.txt file stay empty

private static void prinResults(Process process) throws IOException {
		// TODO
		FileWriter fw = new FileWriter("result.txt");
		BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
		String line = "";
		int counter = 0;
		while ((line = reader.readLine()) != null) {
			counter++;
			System.out.println("Line " + counter + " " + "  " + line);
			fw.write(line + "\n");
		}
	}