ArrayList集合数据排序问题

核心方法就是使用Collections的sort方法

Collections.sort(comparator ,  mList);

让 Student 实现Comparable接口，或是实例化一个比较器，现在用 Comparator 比较器实例来做一个。

mport java.util.ArrayList;import java.util.Collections;import java.util.Comparator;public class ComparableTest { public static void main(String[] args) {    Comparator<Student> comparator = new Comparator<Student>(){     public int compare(Student s1, Student s2) {      //先排年龄      if(s1.age!=s2.age){       return s2.age-s1.age;      }      else{       //年龄相同则按姓名排序       if(!s1.name.equals(s2.name)){        return s2.name.compareTo(s1.name);       }       else{        //姓名也相同则按学号排序        return s2.id-s1.id;       }      }     }    };    Student stu1 = new Student (1,"zhangsan","male",28,"cs");    Student stu2 = new Student (2,"lisi","female",19,"cs");    Student stu3 = new Student (3,"wangwu","male",22,"cs");    Student stu4 = new Student (4,"zhaoliu","female",17,"cs");    Student stu5 = new Student (5,"jiaoming","male",22,"cs");    ArrayList<Student> List = new ArrayList<Student>();    List.add(stu1);    List.add(stu2);    List.add(stu3);    List.add(stu4);    List.add(stu5);     //这里就会自动根据规则进行排序    Collections.sort(List,comparator);    display(List);   }   static void display(ArrayList<Student> lst){    for(Student s:lst)     System.out.println(s);   }  }  class Student{   int age;   int id;   String gender;   String name;   String cs;   Student(int id,String name,String gender,int age,String cs){    this.age=age;    this.name=name;    this.gender=gender;    this.id=id;    this.cs=cs;   }   public String toString(){    return id+"  "+name+"  "+gender+"  "+age+"  "+cs;   }  }