protected boolean canCompare(final Geocache cache) {
        return true;
    }
Check necessary preconditions (like missing fields) before running the comparison itself.
Caches not filling the conditions will be placed last, sorted by Geocode.
<br>
The default implementation returns {@code true} and can be overridden if needed in sub classes.

@param cache the cache to be sorted
@return {@code true} if the cache holds the necessary data to be compared meaningfully
main/src/main/java/cgeo/geocaching/sorting/AbstractCacheComparator.java