java - 如何将静态变量调用到非静态方法，即我需要调用 maxId 变量来插入方法

Question

public static List<Movie> movies;

static {
    movies = new ArrayList<>();
    movies.add(new Movie(1, "Fprd vs Ferrari", "Movie on Racing", "abcd", "xyz"));
    movies.add(new Movie(2, "F2", "Comedy Movie", "Venkatesh", "Tamanna"));
    movies.add(new Movie(3, "Titanic", "Movie", "Hero", "Heroine"));
    Movie max = Collections.max(movies, Comparator.comparingInt(Movie::getId));
    int maxId = max.getId();

}

public Result insert(Http.Request request) {
        JsonNode jsonNode = request.body().asJson();
        if (jsonNode == null) {
            return badRequest("insufficient movie information");
        }
                Movie movie = Json.fromJson(jsonNode, Movie.class);
               movies.add(movie);
               return ok(Json.toJson(movie));

    }

这是插入方法。现在我想访问 maxId 变量以插入方法。任何人都可以告诉我如何清除这个以增加 id

Answer 1

你不能。这是一个局部变量。

这也不是静态方法，而是静态 block 。它在类第一次加载到内存中时执行，之后不再执行。如果您想保留该值，请将代码更改为:

private static int maxId;

static {
    movies = new ArrayList<>();
    movies.add(new Movie(1, "Fprd vs Ferrari", "Movie on Racing", "abcd", "xyz"));
    movies.add(new Movie(2, "F2", "Comedy Movie", "Venkatesh", "Tamanna"));
    movies.add(new Movie(3, "Titanic", "Movie", "Hero", "Heroine"));
    Movie max = Collections.max(movies, Comparator.comparingInt(Movie::getId));
    maxId = max.getId();
}

编辑

您可以做的是将最后两行提取到实际方法(静态方法或实例方法):

public static int getMaxId() {
    Movie max = Collections.max(movies, Comparator.comparingInt(Movie::getId));
    return max.getId();
}

并像调用任何其他方法一样调用此方法。