compareTo

 String的compareTo其实就是依次比较两个字符串ASC码。如果两个字符的ASC码相等则继续后续比较，否则直接返回两个ASC的差值。如果两个字符串完全一样，则返回0.

//需要进行排序的字符串
String[] array = new String[] { "lilei", "libai", "james", "poly",
    "wobfei" };
//使用简单的循环排序
  for (int i = 0; i < array.length - 1; i++) {
   for (int j = i + 1; j < array.length; j++) {
    if (array[i].compareTo(array[j]) > 0) {
     String temp = array[i];
     array[i] = array[j];
     array[j] = temp;
    }
   }
  }

 

排序后：

james  libai  lilei  poly  wobfei

 

 

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
 
class User {
  String name;
  String age;
 
  public User(String name,String age){
   this.name=name;
   this.age=age;
  }
  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;
  }
 }

 

 

 class ComparatorUser implements Comparator{

  public int compare(Object arg0, Object arg1) {
   User user0=(User)arg0;
   User user1=(User)arg1;

    //首先比较年龄，如果年龄相同，则比较名字

   int flag=user0.getAge().compareTo(user1.getAge());
   if(flag==0){
    return user0.getName().compareTo(user1.getName());
   }else{
    return flag;
   } 
  }
 
 }

 

 //测试类
 public class SortTest {

 
  public static void main(String[] args){
   List userlist=new ArrayList();
   userlist.add(new User("dd","4"));
   userlist.add(new User("aa","1"));
   userlist.add(new User("ee","5"));
   userlist.add(new User("bb","2")); 
   userlist.add(new User("ff","5"));
   userlist.add(new User("cc","3"));
   userlist.add(new User("gg","6"));
  
   ComparatorUser comparator=new ComparatorUser();
   Collections.sort(userlist, comparator);
   
   for (int i=0;i<userlist.size();i++){
    User user_temp=(User)userlist.get(i);
       System.out.println(user_temp.getAge()+","+user_temp.getName());
   }
  
  }
 }