Collections sort 降序

public class User implements Comparable<User> {

    private long id;
    private int age;

    public User(long id, int age) {
        this.id = id;
        this.age = age;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public int compareTo(User obj) {
        if (this.age > obj.age) {
            return 1;
        } else if (this.age < obj.age) {
            return -1;
        }
        return 0;
    }

    @Override
    public String toString() {
        return "User [id=" + id + ", age=" + age + "]";
    }

}

public class Test {
    public static void main(String[] args) {
        List<User> list = new ArrayList<User>();
        list.add(new User(1, 3));
        list.add(new User(1, 2));
        list.add(new User(1, 4));
        Collections.sort(list);
        Collections.reverse(list);
        System.err.println(list);
    }
}