// R Function<T,R>
Function<String,Integer> function  = s -> {return s.length();};
System.out.println(function.apply("abc"));

// boolean Predicate<T>
Predicate<String> predicate = s ->{return s.isEmpty();};
System.out.println("rin");

// void Consumer<T>
Consumer<String> consumer = s -> {
System.out.println("its consumer");
};
consumer.accept("rin");

// T Supplier<T>
Supplier<String> supplier = ()->{return "supplier return";};
System.out.println(supplier.get());

@Data
@NoArgsConstructor
@AllArgsConstructor
class User{
    private Integer id;
    private String userName;
    private int age;
}

/**
 * 题目：请按照给出的数据，找出同时满足以下条件的用户，也即以下条件全部满足偶数ID且年龄大于24
 * 且用户名转为大写且用户字母倒排序
 * 只输出一个用户名字
 * */
public class StreamDemo {
    public static void main(String[] args) {
        User u1 = new User(11,"aa",23);
        User u2 = new User(12,"bb",28);
        User u3 = new User(13,"cc",22);
        User u4 = new User(14,"dd",28);
        User u5 = new User(16,"ee",26);

        List<User> list = Arrays.asList(u1, u2, u3, u4, u5);

        // Stream<T> filter(Predicate<? super T> predicate);  过滤器
        // <R> Stream<R> map(Function<? super T, ? extends R> mapper);  映射
        list.stream().filter(user->{return user.getId()%2==0;}) // 偶数ID 过滤器
                .filter(user -> {return user.getAge()>24;}) // 年龄大于24过滤器
                .map(u->{return u.getUserName().toUpperCase();}) // 用户名转为大写,返回值变成Steam<String>了
                .sorted((o1,o2)->{return o2.compareTo(o1);}) // 用户字母倒排序
                .limit(2) // 限制个数
                .forEach(System.out::println);
    }
}