public static void main(String[] args) throws FileNotFoundException {


        TreeSet set = new TreeSet();

        set.add(new Student("zhangsan",12));
        set.add(new Student("lisi",85));
        set.add(new Student("lisi2",85));
        set.add(new Student("wangwu",42));
        set.add(new Student("zhaoliu",45));

        for (Object o : set) {
            System.out.println(o);
        }
}

class Student implements Comparable<Student>{
    String name;
    int age;

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    public Student() {
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

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

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Student student = (Student) o;
        return age == student.age && Objects.equals(name, student.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, age);
    }

    @Override
    public int compareTo(Student o) {
        return o.age-this.age;
    }
}