按List中对像某属性排序算法1---实现Comparator接口

按List中Person类的age属性进行排序。

 

Person类：

package com.flg;

/**
 * Created with IntelliJ IDEA.
 * User: fuliguo
 * Date: 12-7-29
 * Time: 下午12:35
 * To change this template use File | Settings | File Templates.
 */
public class Person {

    private String name;
    private int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }


}

 

 

MyPersonListSortTest1：

package com.flg;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * Created with IntelliJ IDEA.
 * User: fuliguo
 * Date: 12-7-29
 * Time: 下午12:34
 * To change this template use File | Settings | File Templates.
 */
public class MyPersonListSortTest1 implements Comparator {

    private boolean isAsc; //是否升序排列

    public boolean isAsc() {
        return isAsc;
    }
    //带升降顺序设置的构造参数
    public MyPersonListSortTest1(boolean asc) {
        isAsc = asc;
    }

    //无参构造函数
    public MyPersonListSortTest1(){}

    /**
     * 获得要测试的list
     * @return   list
     */
    public List getList(){

        List list  = new ArrayList<Person>() ;

        Person p1 = new Person();
        p1.setName("张三");
        p1.setAge(10);

        Person p2 = new Person();
        p2.setName("李四");
        p2.setAge(20);

        Person p3 = new Person();
        p3.setName("王五");
        p3.setAge(30);

        //打乱存放顺序
        list.add(p2);
        list.add(p1);
        list.add(p3);


        return list;

    }

    /**
     * 控制台输出遍历list对像顺序
     * @param list
     */
    public  void printList(List list){
        Person p;
        for(int i=0;i<list.size();i++){
            p = (Person)list.get(i);
            System.out.println(p.getName()+"---"+p.getAge());
        }
    }

    /**
     * 对list进行排序
     * @param list
     */
    public void listSort(List list,boolean isAsc){
        Collections.sort(list, (Comparator) new MyPersonListSortTest1(isAsc));

    }

    /**
     * 当前类实现了Comparator接口的compare方法
     * 站在第三方角度去比较其它对象
     * 是一个Comparator的角色
     * @param p1
     * @param p2
     * @return
     */
    @Override
    public int compare(Object p1, Object p2) {
        if(isAsc()){
            return ((Person)p1).getAge()-((Person)p2).getAge();
        }else {
            return ((Person)p2).getAge()-((Person)p1).getAge();
        }

    }


    public static void main(String [] args){

        MyPersonListSortTest1 m = new MyPersonListSortTest1();

        List list = m.getList();
        System.out.println("==========排序前=========");
        m.printList(list);

        m.listSort(list,false); //排序isAsc:true 升序，false:降序
        System.out.println("==========排序后=========");
        m.printList(list);

    }
}