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基于Comparator對(duì)象集合實(shí)現(xiàn)多個(gè)條件按照優(yōu)先級(jí)的比較

更新時(shí)間：2021年07月12日 09:25:41 作者：CoderYin

這篇文章主要介紹了基于Comparator對(duì)象集合實(shí)現(xiàn)多個(gè)條件按照優(yōu)先級(jí)的比較，具有很好的參考價(jià)值，希望對(duì)大家有所幫助。如有錯(cuò)誤或未考慮完全的地方，望不吝賜教

一、背景介紹

在日常的java開(kāi)發(fā)中，我們?cè)诜祷匾粋€(gè)對(duì)象集合時(shí)需要按照對(duì)象的某個(gè)屬性或者某些屬性進(jìn)行排序返回給前端進(jìn)行展示，例如我最近需要返回一個(gè)題庫(kù)集合，需要先根據(jù)指定時(shí)間排序然后根據(jù)創(chuàng)建時(shí)間進(jìn)行排序，在mysql層進(jìn)行操作比較麻煩而且浪費(fèi)時(shí)間，我們可以通過(guò)程序來(lái)進(jìn)行排序。

二、案例代碼

// 實(shí)體類
public class People {
	private Integer id;
	private String name;
	private Integer topTime;// 置頂時(shí)間
	private Integer gmtCreate;// 創(chuàng)建時(shí)間 
	public People(Integer id, String name, Integer topTime, Integer gmtCreate) {
		super();
		this.id = id;
		this.name = name;
		this.topTime = topTime;
		this.gmtCreate = gmtCreate;
	}
 
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Integer getTopTime() {
		return topTime;
	}
	public void setTopTime(Integer topTime) {
		this.topTime = topTime;
	}
	public Integer getGmtCreate() {
		return gmtCreate;
	}
	public void setGmtCreate(Integer gmtCreate) {
		this.gmtCreate = gmtCreate;
	}
 
	@Override
	public String toString() {
		return "People [id=" + id + ", name=" + name + ", topTime=" + topTime + ", gmtCreate=" + gmtCreate + "]";
	}
}

// 排序方法
public class PeopleComparator implements Comparator<People>{
 
	@Override
	public int compare(People o1, People o2) {
		int result = 0;
		// 按照置頂時(shí)間排序升序(o1,o2位置互換就是降序)
		int topTimeSeq = o2.getTopTime() - o1.getTopTime();
		if(topTimeSeq != 0){
			result = (topTimeSeq > 0) ? 3 : -1;
		}else{
			// 按照創(chuàng)建時(shí)間排序
			topTimeSeq = o2.getGmtCreate() - o1.getGmtCreate();
			if(topTimeSeq != 0){
				result = (topTimeSeq > 0) ? 2 : -2;
			}
		}
		return result;
	}
}

// 測(cè)試
public class PeopleTest {
	public static void main(String[] args) {
		List<People> peopleList = new ArrayList<People>(){
			{
				add(new People(1,"tom1",0,1));
				add(new People(2,"tom2",2,4));
				add(new People(3,"tom3",1,3));
				add(new People(4,"tom4",0,6));
				add(new People(5,"tom5",0,2));
				add(new People(6,"tom6",0,5));
			}
		};
		Collections.sort(peopleList,new PeopleComparator());
		for(People p:peopleList){
			System.out.println(p.toString());
		}
	}
}

測(cè)試結(jié)果

Comparator 多條件比較

class Card {
    int a;
    int b;
    public Card(int a, int b) {
        this.a = a;
        this.b = b;
    }
    public int getA() {
        return a;
    }
    public int getB() {
        return b;
    }
    @Override
    public String toString() {
        return "Card{" +
                "a=" + a +
                ", b=" + b +
                '}';
    }
}
public class Main {
    public static void main(String[] args) {
        List<Card> list = new ArrayList<>();
        list.add(new Card(0, 2));
        list.add(new Card(1, 1));
        list.add(new Card(1, 0));
        list.add(new Card(1, 0));
        list.add(new Card(2, 0));
        System.out.println(list);
        System.out.println();
        
        Collections.sort(list, new Comparator<Card>() {
            @Override
            public int compare(Card c1, Card c2) {
                // c1 - c2  升序
                // c2 - c1  降序
                int res1 = c2.b - c1.b;
                int res2 = c2.a - c1.a;
                // 當(dāng) b相等時(shí)比較a, 否則先比較b
                return res1 == 0 ? res2 : res1;
            }
        });
        System.out.println(list);
    }
}
[Card{a=0, b=2}, Card{a=1, b=1}, Card{a=1, b=0}, Card{a=1, b=0}, Card{a=2, b=0}]
[Card{a=0, b=2}, Card{a=1, b=1}, Card{a=2, b=0}, Card{a=1, b=0}, Card{a=1, b=0}]

以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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