public SortedBin next() {
            if (next == null) {
                next = new SortedBin(binsize << 1, parent);
            }
            return next;
        }
add a key value pair to the heap

@param key   the key to insert
@param value the value to insert object
main/src/main/java/cgeo/geocaching/brouter/util/SortedHeap.java