Collections.sort 重写compare（）方法

Comparator是个接口，主要比的是两个对象,比较规则是自己写的，可以重写他的compare（）和equals（）这两个方法，也就是说比较的方法。如果是Null的话，就是使用元素的自然顺序，如1 3 2 4就是1 2 3 4 。字母也可以compare（a,b）方法:根据第一个参数小于、等于或大于第二个参数分别返回负整数、零或正整数。

Test.java

package com.djcken;import java.util.ArrayList;import java.util.Collections;import java.util.List;import com.djcken.UserBean.ComparatorUser;public class Test {public static void main(String[] args){             List userlist=new ArrayList();               userlist.add(new UserBean("d","1"));               userlist.add(new UserBean("a","4"));               userlist.add(new UserBean("e","5"));               userlist.add(new UserBean("b","2"));                 userlist.add(new UserBean("f","5"));               userlist.add(new UserBean("c","3"));               userlist.add(new UserBean("g","6"));                              ComparatorUser comparator= new ComparatorUser();           Collections.sort(userlist, comparator);                               for (int i=0;i<userlist.size();i++){               UserBean user_temp=(UserBean)userlist.get(i);                   System.out.println(user_temp.getAge()+","+user_temp.getName());                }                  }             }

UserBean.java

package com.djcken;import java.util.Comparator;public class UserBean{private String age;private String name;public UserBean(String age, String name) {super();this.age = age;this.name = name;}public String getAge() {return age;}public void setAge(String age) {this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}public static class ComparatorUser implements Comparator{public int compare(Object o1, Object o2) {UserBean user0 = (UserBean) o1;UserBean user1 = (UserBean) o2;int thislv = user0.getAge().compareTo(user1.getAge());if (thislv == 0) {return user0.getName().compareTo(user1.getName());} else {return thislv;}}} }

结果：

1,d
2,b
3,c
4,a
5,e
5,f
6,g