java - memory usage

A String uses 48 bytes plus the size of the text * 2. (Each character is 2 bytes) The Simple Cell object uses 40 bytes and the List of them uses 1064 bytes.

This means each row uses 1064 + 160 * 40 + 5 * 180 * (48 + 20) bytes or about 68K. If you have 1000 lines you will be using about 70 MB which is much less than what you are seeing.

I suggest you use a memory profile to see exactly how much memory is being used by what. e.g. VisualVM or YourKit.

Depending on how you construct the Strings you retain even more memory than this. For example its likely you are retaining a reference to the original XML as when you take a substring of it, you are actually holding a copy of the original.

You may find this class useful. It will reduce the amount of memory Strings use if they are using more than they need and reduce duplicates using a fixed size cache.

static class StringCache {
    final WeakReference<String>[] strings;
    final int mask;

    @SuppressWarnings("unchecked")
    StringCache(int size) {
        int size2 = 128;
        while (size2 < size)
            size2 *= 2;
        strings = new WeakReference[size2];
        mask = size2 - 1;
    }

    public String intern(String text) {
        if (text.length() == 0) return "";

        int hash = text.hashCode() & mask;
        WeakReference<String> wrs = strings[hash];
        if (wrs != null) {
            String ret = wrs.get();
            if (text.equals(ret))
                return ret;
        }
        String ret = new String(text);
        strings[hash] = new WeakReference<String>(ret);
        return ret;
    }
}