容器的排序-3

下面通过实例来具体使用Comparator和Comparable

public class Goods {
    private String name;
    private double price;
    private int fav;

    public Goods() {
    }
    public Goods(String name, double price, int fav) {
        super();
        this.name = name;
        this.price = price;
        this.fav = fav;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
    public int getFav() {
        return fav;
    }
    public void setFav(int fav) {
        this.fav = fav;
    }

    //这里需要重写Object中的toString方法，因为正常的toString方法如下：
    //public String toString() {
    //    return getClass().getName() + "@" + Integer.toHexString(hashCode());
    //}

    @Override
    public String toString() {
        return this.name+"--"+this.price+"--"+this.fav;
    }
}

import java.util.Comparator;
//因为对于商品的要求不一样，有些人希望按照价格来排列，有些人希望按照人气指数来排，所以
//使用Comparator的好处在于解耦，也就是同步工作，互不干扰，这里按照价格来排序，当然也
//也可以按照其他的来排序
public class Goodsprice implements Comparator<Goods>{
    @Override
    public int compare(Goods o1, Goods o2) {
        //按照升序排序，前面加负号表示为降序，其实正常应该这么写：
        // return -(o1.getPrice()-o2.getPrice()>0?1:(o1.getPrice()==o2.getPrice()?0:-1));
        return (int) -(o1.getPrice()-o2.getPrice());
    }
}

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

public class GoodsAPP {
    public static void main(String[] args) {
        List<Goods> list = new ArrayList<>();
        list.add(new Goods("苹果", 10, 6));
        list.add(new Goods("梨子", 12, 8));
        list.add(new Goods("桃子", 12, 7));
        list.add(new Goods("栗子", 20, 3));
        list.add(new Goods("香蕉", 18, 10));
        Collections.sort(list,new Goodsprice());
        System.out.println(list);
    }   
}

输出结果为：[栗子--20.0--3, 香蕉--18.0--10, 梨子--12.0--8, 桃子--12.0--7, 苹果--10.0--6]

import java.text.DateFormatSymbols;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
/**
 * 对于新闻，按照顺序，时间降序，点击量升序，标题降序
 * 使用Comparable的顺序就是已经订好的
 * @author Administrator
 */
public class NewsItem implements Comparable<NewsItem>{
    private String title;
    private int hit;
    private String time;

    public NewsItem() {
    }
    public NewsItem(String title, int hit,  String time) {
        super();
        this.title = title;
        this.hit = hit;
        this.time = time;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public int getHit() {
        return hit;
    }

    public void setHit(int hit) {
        this.hit = hit;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    @Override
    public int compareTo(NewsItem o) {
        int result = 0;
        result = -this.time.compareTo(o.time);
        if(result==0){
            result = this.hit-o.hit;  //因为是int类型，所以直接相减，不能使用compareTo方法
            if(result==0){
                result = this.title.compareTo(o.title);
            }
        }
        return result;
    }

    @Override
    public String toString() {

        try {
            return this.title+"--"+this.hit+"--"+new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse(time).toLocaleString()+"\n";
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return null;
    }   
}

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

public class NewsApp {
    public static void main(String[] args) {
        List<NewsItem> list = new ArrayList<>();
        list.add(new NewsItem("LPL夺冠了",1000,"2020-9-19 17:20:00"));
        list.add(new NewsItem("LMS夺冠了",10,"2050-9-23 18:20:00"));
        list.add(new NewsItem("LCK夺冠了",800,"2017-9-23 19:20:00"));
        Collections.sort(list);
        System.out.println(list);
    }
}

输出结果：[LMS夺冠了--10--2050-9-23 18:20:00
    , LPL夺冠了--1000--2020-9-19 17:20:00
    , LCK夺冠了--800--2017-9-23 19:20:00
    ]