arraylist如何在给定某个参数的情况下返回java中的多个对象

Question

下面的方法接收来自用户的starRating，并搜索数组以匹配该评级。当值与其中一个对象匹配时，它应该返回它。尽管该方法有效，但它只返回一个它找到的Movie对象，而不是每个对象。例如，如果我输入3，它会返回第一部星级为3的电影，然后什么也不做。此外，如果星级不存在，我如何返回空列表？我做了一些研究，但似乎找不到任何有用的东西。谢谢

/**
 * Write a method that returns a list of movies with the given star rating.
 * Return an empty list if the star rating does not exist.
 */
public Movie getMoviesWithRating(int rating)
{
    for (Movie movies : movies){
        if(movies.getStarRating() == rating){
            return movies;
        }
    }
    return //EmptyList
}

Answer 1

要返回电影列表，必须具有列表的返回类型

public List<Movie> getMoviesWithRating(int rating)
{
    List<Movie> movies = new ArrayList<Movie>();
    for (Movie movies : movies){
        if(movies.getStarRating() == rating){
            movies.add(movie);
        }
    }
    return movies.
}

如果无法更改返回类型，至少如果找不到具有给定评级的电影，则返回空值

public Movie getMoviesWithRating(int rating)
{
    for (Movie movies : movies){
        if(movies.getStarRating() == rating){
            return movie;
        }
    }
    return null.
}

Answer 2

如果你有Java 8，你可以这样做：

public List<Movie> getMoviesWithRating(int rating) {
    return movies.stream().filter(movie -> movie.rating == rating).collect(Collectors.toList());
}

Answer 3

你可以在下面尝试：

public List<Movie> getMoviesWithRating(int rating)
{
    List<Movie> movies = new ArrayList<Movie>();
    for (Movie movies : movies){
        if(movies.getStarRating() == rating){
            movies.add(movie);
        }
    }
    return movies.
}

如果您正在使用Java 8，您可以尝试：

public List<Movie> getMoviesWithRating(int rating) {
    return movies.stream().filter(movie -> movie.rating == rating).collect(Collectors.toList());
}

如果找不到项，更好的方法可能是抛出exception：

public Movie getMoviesWithRating(int rating){
    for(final Movie movie : Movie){
         if (movie.getRating() == rating) {
             return movie;
         }
    }
    throw new NoSuchElementException();
}

Answer 4

This Might help u out to build your Logic. Thank You.. Hope for d best :)

 public ArrayList<Movie> getMoviesWithRating(int rating)
    {
      ArrayList<Movie> obj_arrMovie = new ArrayList<Movie>();
        for (Movie obj_movies : movies){ //Iterate throughout the movies Array.
            if(obj_movies.getStarRating() == rating){ //Conditional Statement to check whether it is equivalent to rating or not ?.
                 obj_arrMovie.add(obj_movies); //Add all movie object to arraylist which can pass the condition.
            }
        }
        return obj_arrMovie;
    }