Comparable接口实现集合的排序

1.让需要排序的对象实现Comparable接口，并重写compareTo方法

public class Student implements Comparable<Student> {　　//泛型为需要排序的对象    
    private int age;
　　 private String name;
    private int score;
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getScore() {
        return score;
    }
    public void setScore(int score) {
        this.score = score;
    }
    public Student(int age, String name, int score) {
        super();
        this.age = age;
        this.name = name;
        this.score = score;
    }

    @Override
    public int compareTo(Student other) {　　　　//参数为需要排序的对象
        return score-other.getScore();　　//表示通过分数score字段进行排序
    }
}

2.构造需要排序的对象的集合，并调用Collections.sort()方法对集合中元素进行排序：

public class CompareTest {

    public static void main(String[] args) {
        Student s1 = new Student(16, "aa", 44);
        Student s2 = new Student(18, "bb", 88);
        Student s3 = new Student(17, "cc", 99);
        Student s4 = new Student(19, "dd", 66);

        List<Student> students = Arrays.asList(s1, s2, s3, s4);

        Collections.sort(students);　　//对students按score字段进行排序  

        for (Student student : students) {
            System.out.println(student.getScore());
        }
    }
}

注意：使用 Collections.sort(students);方法对集合对象进行排序时，集合中的对象必须实现Comparable接口，否则报错