@Override
public int compareTo(Item another) {
int comp1 = 0;
if (getCategory() != null && another.getCategory() != null)
comp1 = getCategory().compareToIgnoreCase(another.getCategory());
else if (getCategory() == null) comp1 = -1;
else if (another.getCategory() == null) comp1 = 1;
else comp1 = 0;
int comp2 = getName().compareToIgnoreCase(another.getName());
int comp3 = getId().compareTo(another.getId());
return comp1 * 10000 + comp2 * 100 + comp3;
}