java 对象排序，根据多个字段进行排序

package comparotor;

import java.sql.Date;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Random;

import org.apache.commons.beanutils.BeanComparator;
import org.apache.commons.collections.ComparatorUtils;
import org.apache.commons.collections.comparators.ComparableComparator;
import org.apache.commons.collections.comparators.ComparatorChain;

public class Comparotor
{
public static void main(String[] args)
{
Comparator mycmp1 = ComparableComparator.getInstance ();  
mycmp1 = ComparatorUtils. reversedComparator(mycmp1); //逆序  

Comparator mycmp2 = ComparableComparator.getInstance ();  
//mycmp2 = ComparatorUtils. reversedComparator(mycmp2); //允许null  
mycmp2 = ComparatorUtils. nullHighComparator(mycmp2); //允许null  

// 声明要排序的对象的属性，并指明所使用的排序规则，如果不指明，则用默认排序  
ArrayList<Object> sortFields = new ArrayList<Object>();  
sortFields.add( new BeanComparator("age" , mycmp1)); //主排序（第一排序）  
sortFields.add( new BeanComparator("birthday" , mycmp2)); //次排序（第二排序）  

// 创建一个排序链  
ComparatorChain multiSort = new ComparatorChain(sortFields);  
List<User> users = initUsers();  
// 开始真正的排序，按照先主，后副的规则  
Collections.sort (users , multiSort);
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>");
for(int i =0;i<10;i++){
User user = users.get(i);
System.out.println(user.getName()+"---"+user.getSex()+"---"+user.getAge()+"---"+user.getBirthday());
}
}

private static List<User> initUsers(){
List<User> list = new ArrayList<User>();
for(Integer i =0;i<10;i++){
Random rm = new Random();
User user = new User();
user.setName("user"+i);
user.setAge(rm.nextInt(10));
if(i%2==0){
user.setSex("1");
}else{
user.setSex("0");
}
user.setBirthday(new Date(2014,11,21));
if(i==5){
user.setBirthday(new Date(2014,11,20));
user.setSex(null);
}
System.out.println(user.getName()+"---"+user.getSex()+"---"+user.getAge()+"---"+user.getBirthday());
list.add(user);
}
return list;
}
}