Cheap string building/formatting for inputstreams and timer displays?

I am having a fair amount of memory problems with my app. I think I have my bitmaps sorted out, my current problem seems to stem from String开发者_如何学运维s. I have 2 functions that happen often and need to make sure they are solid.

First is converting an inputstream to a string.

The second one is to format a timer display as in a mediaplayer. This happens every second.

Are there any obvious inefficiencies in these functions?? Thanks

**edit, did a quick edit of the maketimestring, for an obvious inneficiency I spotted where I was pulling a string from resources every time.

    private static StringBuilder sBuilder = new StringBuilder();
    private static Formatter sFormatter = new Formatter(sBuilder, Locale.getDefault());
    private static final Object[] sTimeArgs = new Object[5];

    public static String makeTimeString(String durationFormat, long secs) {
        sBuilder.setLength(0);
        final Object[] timeArgs = sTimeArgs;
        timeArgs[0] = secs / 3600;
        timeArgs[1] = secs / 60;
        timeArgs[2] = (secs / 60) % 60;
        timeArgs[3] = secs;
        timeArgs[4] = secs % 60;
        return sFormatter.format(durationformat, timeArgs).toString();
    }

    public static String formatContent(InputStream is) throws IOException {
        if (is == null) 
            return "";

        sBuilder.setLength(0);
        BufferedReader buffer = new BufferedReader(new InputStreamReader(is));
        String line = null;
        while ((line = buffer.readLine()) != null) {
            sBuilder.append(line).append("\n");
        }
        buffer.close();
        buffer = null;

        return sBuilder.toString().trim();
    }

Keeping the StringBuilder as a class variable means that its internal buffer stays allocated for the life of the class. Unless you need the character data as both a StringBuilder and a String, you should create a new StringBuilder as a local variable inside formatContent() each time it is called. Alternatively, if you can make do with a CharSequence instead of a String, and just use the StringBuilder instead of constructing a String. (That doesn't work, of course, if you have to eventually pass it to an API outside your control that requires a String.)