java函数式编程stream流操作lambda表达式使用方法引用用法等练习

java函数式编程stream流操作lambda表达式使用方法引用用法等练习

    @Test
    void test01() {
        System.out.println("111");
        List<Author> authors = getAuthor();
        //stream流打对象中一个字段
        authors.stream().distinct().forEach(author -> System.out.println(author.name));

        //flatMap把一个stream流转成另一个stream流,然后通过map转成对象，最终在转成list
        //把书名放到一个list中
        List<String> name_list = authors.stream().flatMap(author -> author.books.stream()).map(books -> books.name).collect(Collectors.toList());

        System.out.println(name_list);
    }


    @Test
    public void test02(){
        List<Author> authors = getAuthor();

        //引用类的实例方法 System.out::print
        //打印出所有书名
        authors.stream().flatMap(author -> author.books.stream()).map(books -> books.name).forEach(System.out::print);
    }



    public static  List<Author> getAuthor(){
        List<Books> books1 = new ArrayList<Books>() {
            {
                add(new Books(1,"书1","小说,科学",10,"简介一11"));
                add(new Books(2,"书2","计算机,理财",20,"简介一20"));
                add(new Books(3,"书3","屋里,科学",30,"简介一30"));
                add(new Books(4,"书4","化学,经济",40,"简介一40"));
                add(new Books(5,"书5","小说,科学",50,"简介一50"));
            }
        };

        List<Books> books2 = new ArrayList<Books>() {
            {
                add(new Books(6,"书6","小说,科学",60,"简介一61"));
                add(new Books(7,"书7","计算机,理财",70,"简介一70"));
                add(new Books(8,"书8","屋里,科学",80,"简介一80"));
            }
        };

        List<Books> books3 = new ArrayList<Books>() {
            {
                add(new Books(9,"书9","小说,科学",90,"简介一90"));
                add(new Books(10,"书10","计算机,理财",100,"简介一100"));
            }
        };

        List<Author> authors = new ArrayList<Author>(){
            {
                add(new Author(1,"作者1",11,books1));
                add(new Author(2,"作者2",22,books2));
                add(new Author(3,"作者3",33,books3));
            }
        };
        return authors;

    }



    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public static class Author {
        public Integer id;
        public String name;
        public Integer age;
        public List<Books> books;
    }


    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public static class Books {
        public Integer id;
        public String name;
        public String category;
        public Integer socre;
        public String intro;
    }

参： https://www.bilibili.com/video/BV1Gh41187uR