private void ensureContentIndexListIndexMap() {
        if (categories.isEmpty() || !contentIndexListIndexMap.isEmpty()) {
            return;
        }

        int contentPos = 0;
        int catCounter = 0;
        for (String cat : categories) {
            catCounter++;
            contentIndexListIndexMap.put(contentPos, catCounter);
            contentPos += categoryCounts.get(cat);
        }
    }
gets number of content entries in the list
main/src/main/java/cgeo/geocaching/utils/CategorizedListHelper.java