//对象类型stream排序List<User> users = new ArrayList<User>(){    {        add(new User("a", "1983/12/24", 36));        add(new User("a", "1993/12/24", 26));        add(new User("a", "1973/12/24", 46));        add(new User("a", "1995/12/24", 24));        add(new User("a", "1981/12/24", 38));        add(new User("a", "1991/12/24", 28));    }};

//升序List<User> ascUsers = users.stream().sorted(Comparator.comparing(User :: getAge)).collect(Collectors.toList());

//降序List<User> descUsers = users.stream().sorted(Comparator.comparing(User :: getAge).reversed()).collect(Collectors.toList());用户类：必须继承Comparable接口，否则排序调用Comparator.comparing的时候会报错，这点很重要。

public class User implements Comparable<User> {

    @NotNull    private String name;

    @Format(value="YYYY-MM-DD", message = "字符串格式不正确")    private String birthday;

    private int age;

    public User(){    }

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

    public String getBirthday() {        return birthday;    }

    public void setBirthday(String brithday) {        this.birthday = birthday;    }

    /**     * 两个相同类型的对象，比较多属相是否相等的时候     * 可以通过重写equals方法来实现     * @param object     * @return     */

    @Override    public boolean equals(Object object) {        if (object instanceof User) {            return this.name.equals(((User) object).getName()) && this.age == ((User) object).getAge();        } else {            return false;        }    }

    /**     * 重写 equals 就应当重写 hashcode     * 因为当两个对象hashcode 值相等，但是 equals 比较为 false，     * 那么在 HashMap 中会产生链表，影响查询性能     * @return     */    @Override    public int hashCode() {        return  this.name.hashCode() + age;    }

    @Override    public int compareTo(User user) {        return name.compareTo(user.getName());    }}