MultiComparator

Quando você escreve um SQL para retornar informações do banco de dados de forma ordenada por vários campos, você escreve algo mais ou menos assim:

ORDER BY nome, idade, codigo

E em Java como você reproduz esta funcionaliade?

Eu faço assim ó :D

/**
 * You can easily combine the results from several Comparators for an object
 * class into one Comparator.
 * 

 *
 * You have the multi-comparator, and individual comparators for all the fields,
 * you can create a comparator that has any properties you want. For example, to
 * sort on EmployeeID, Name, and Age, in that order, you would do this:
 * 

 *
 * 

 * MultiComparator mc = new MultiComparator();
 * mc.add(new EmployeeIdComparator(MyENum.ASC));
 * mc.add(new EmployeeNameComparator(MyENum.ASC));
 * mc.add(new EmployeeAgeComparator(MyENum.DESC));
 * Collections.sort(list, mc);
 *
 */
public class MultiComparator implements Comparator < book > {
 private List<comparator < book > comparatorList;

 public MultiComparator() {
  comparatorList = new ArrayList<comparator<book>>();
 }

 public void addComparator(Comparator<book> c) {
  comparatorList.add(c);
 }

 public void removeComparator(Comparator<object> c) {
  comparatorList.remove(c);
 }

 public int compare(Book obj1, Book obj2) {
  int result = 0;
  for (Comparator<book> c : comparatorList) {
   result = c.compare(obj1, obj2);

   if (result != 0) {
    break;
   }
  }
  return result;
 }
}