Question

这是我显示书籍类型的代码。在这段代码中，我只需要打印一本书的类型。那么有很多不仅仅是关于SciFi的类型，我们必须打印一种类型的SciFi。感谢。

public Class Catalogue(){

    private List<Movie> moviesAvailable;

    private List<Movie> moviesRented;
    private List<Genre> genres;
    public Catalogue(){
        moviesAvailable = new LinkedList<Movie>();
        moviesRented = new LinkedList<Movie>();
        genres = new LinkedList<Genre>();
        moviesAvailable.add(new Movie("Matrix",1999,new Genre("SciFi"),3));
        moviesAvailable.add(new Movie("Jurassic Park",1993, new Genre("SciFi"),4));
        moviesAvailable.add(new Movie("The conjuring",1993, new Genre("Horror"),4));

    }
    private getOnlyGenres(){
        System.out.print("The library has the following genres:")
        for(Genre genre:moviesAvailable){
            System.out.print(genre.toString());
        }
    }

}

Answer 1

你需要改变一些事情：

如果Movie课程没有，请添加Movie课程。
当您遍历电影列表时，会得到Genre个对象，而不是for(Genre genre:moviesAvailable){。这意味着您需要更改：
```
for(Movie movie : moviesAvailable){
```
到
```
Genre
```
现在从每个Movie获取Set并将其添加到List而不是{{1}}。

Answer 2

以下是删除了一些额外列表的工作示例：

import java.util.*;

class Test {
    public static void main(String[] args) {

        List<Movie> moviesAvailable;

        moviesAvailable = new LinkedList<Movie>();

        moviesAvailable.add(new Movie("Matrix",1999,new Genre("SciFi"),3));
        moviesAvailable.add(new Movie("Jurassic Park",1993, new Genre("SciFi"),4));
        moviesAvailable.add(new Movie("The conjuring",1993, new Genre("Horror"),4));

        moviesAvailable.stream().map(movie -> movie.getGenre().getName()).distinct().forEach(System.out::println);

    }
}

class Genre {
    private String name;
    public String getName() {
        return this.name;
    }
    public void setName(String name)
    {
        this.name = name;
    }

    public Genre (String name) {
        this.name = name;
    }

}

class Movie {
    private String name;
    private int year;
    private Genre genre;
    private int whatever;

    public Genre getGenre()
    {
        return this.genre;
    }

    public Movie (String name, int year, Genre genre, int whatever) {
        this.name = name;
        this.year = year;
        this.genre = genre;
        this.whatever = whatever;
    }
}

打印本书的类型

2 个答案: