java中Comparable的例子和用法

3.5 Comparable的用法  

马克-to-win：前面讲过进入TreeSet的每个元素是都排了序的，如果被添加的元素是我们自己定义的，就需要告诉TreeSet排序的规则，这个规则就要在Comparable中定义。在下面的例子中， 当我们要往TreeSet中添加我们自己定义的类Worker对象时，就在compareTo中定义排序规则。

例：3.5.1　

/*why in the past never implements Comparable? becasue Integer claas and

String class both implements this Comparable.

java.lang.Object

java.lang.String

All Implemented Interfaces:

CharSequence, Comparable, Serializable

 */

import java.util.*;

//Comparable接口在java.lang包中定义

//定义的方法：

//int compareTo(Object o);

//实现该接口就可以实现按用户定义的自然顺序排列对象。

/*you must implements Comparable,otherwise, when you add the second element into

 the treeset, it will report error, because it will search for Comparable

 interface. */

class Worker implements Comparable {

    int workNum;

    String name;

    int money;

    public Worker(int workNum, String name, int money) {

        this.workNum = workNum;

        this.name = name;

        this.money = money;

    }

    // 按工资排序

    /*

     * public int compareTo(Object o) Returns: a negative integer, zero, or a

     * positive integer as this object is less than, equal to, or greater than

     * the specified object. it looks like that the one that is in front is

     * small. what if two keys are the same? only print out one item.

     */

    public int compareTo(Object o) {

        Worker e = (Worker) o;

        return money - e.money;//到底谁减谁，讲师如想搞清楚，请听配套视频里的仔细分析。

        // return workNum - e.workNum;

    }

}

更多请见：https://blog.csdn.net/qq_43650923/article/details/100831985