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