案例：成绩排序 实现Comparable接口

//先根据学生的成绩降序排序，如果成绩相同再根据年龄升序排序，如果年龄相同再根据名字升序排序

public class ScoreList implements Comparable{

private String name;
private int age;
private int score;

public ScoreList(String name, int age, int score) {
    this.name = name;
    this.age = age;
    this.score = score;
}

@Override
public int compareTo(Object o) {
    ScoreList sl = (ScoreList)o;

    //return sl.score - this.score;          按分数降序排序
    //return this.age - sl.age;              按年龄升序排序
    //return this.name.compareTo(sl.name)  ; 按名字升序排序

    //先按照 分数 再按照 年龄 最后按照 名字 排序
    int result = sl.score-this.score;
    if(result==0){
        result = this.age-sl.age;
    }
    if (result==0){
        result=this.name.compareTo(sl.name);
    }

    return result;
}

}