How to sort a collection based on their date?

Question

how do i sort a collection based on their respective dates which are in Calendar format?

Answer 1

this is my codes
/** This class is use to sort the call list base on their date
import java.util.*;
public class a implements Comparator
     /** compare the objects base on their types
     *     @obj1 the first object to be compared
     *     @obj2 the second object to compare with the first object
     public int compare(Object obj1, Object obj2)
     if (obj1 == obj2)
          return 0;
     if (obj1 == null || obj2 == null)
          return 0;
     if (!(obj1 instanceof Call) || !(obj2 instanceof Call))
          return 0;
     Call lhs = (Call) obj1;
     Call rhs = (Call) obj2;
     int s = lhs.getDate().compareTo(rhs.getDate());
     if (s != 0)     
          return s;
     return 1;
this is the error
a.java:21: cannot resolve symbol
symbol : method compareTo (java.util.Calendar)
location: class java.util.Calendar
     int s = lhs.getDate().compareTo(rhs.getDate());