How to get the content of an input stream in reverse order?

Question

I am using a txt file for my level desing. I use the below to take the contents and convert to string buffer, then iterate through the lines to generate my game objects.

The the problem is that it reads from top down and so I have to design my levels upside down for them to be right way around.

How can I change the stream to read the opposite way? Or write the lines to the String Builder the opposite way?

 private static String convertStreamToString(InputStream is) {

        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();

        String line = null;
        try {
            while ((line = reader.readLine()) != null) {
                sb.append((line + "\n"));
            }
        } catch (IOException e) {
            Log.w("LOG", e.getMessage());
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                Log.w("LOG", e.getMessage());
            }
        }
        return sb.toString();

will the `insert()` method of string builder not suffice? – Oneb May 23 '13 at 08:27 — Oneb, May 23 '13 at 08:27

score 7 · Accepted Answer · answered May 23 '13 at 08:26

7

You could just use sb.insert(0, line + "\n") instead of sb.append(line + "\n");.

This will always add new lines to the front of the string, not append it to the end. Should do exactly what you want and will be just as fast, because StringBuilder is made exactly for things like that.

answered May 23 '13 at 08:26

Till Helge

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Genius. Thanks for that. Sorry to be an idiot, but would you mind briefing explaining why that works? – Rhys May 23 '13 at 08:29
Thanks for taking the time to explain. – Rhys May 23 '13 at 08:33
@Till Helge would that be faster/better than appending to sb then returning sb.reverse().toString() – anthonyms May 23 '13 at 08:40
1

@artfullyContrived No, but it would be correct in comparison. Only the order of the lines is meant to be reversed, not the entire string. – Till Helge May 23 '13 at 08:41

How to get the content of an input stream in reverse order?

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