Lambda end operation collect

collect

​ Convert the current stream into a collection .

Example ：

​ Get a file that holds the names of all authors List aggregate .

//         Get a file that holds the names of all authors List aggregate .
        List<Author> authors = getAuthors();
        List<String> nameList = authors.stream()
                .map(author -> author.getName())
                .collect(Collectors.toList());
        System.out.println(nameList);

Get a list of all book titles Set aggregate .

//         Get a list of all book titles Set aggregate .
        List<Author> authors = getAuthors();
        Set<Book> books = authors.stream()
                .flatMap(author -> author.getBooks().stream())
                .collect(Collectors.toSet());

        System.out.println(books);

Get one Map aggregate ,map Of key Name the author ,value by List<Book>

//         Get one Map aggregate ,map Of key Name the author ,value by List<Book>
        List<Author> authors = getAuthors();

        Map<String, List<Book>> map = authors.stream()
                .distinct()
                .collect(Collectors.toMap(author -> author.getName(), author -> author.getBooks()));

        System.out.println(map);