Question

我似乎无法在Eclipse中运行以下代码。我有一个main方法，这是当前打开的文件。我甚至尝试了“运行方式”选项，但我不断收到此错误：“编辑器不包含主类型”。我在这里做错了什么？

 public class cfiltering {

    /**
     * @param args
     */

    //remember this is just a reference
    //this is a 2d matrix i.e. user*movie
    private static int user_movie_matrix[][];

    //remember this is just a reference
    //this is a 2d matrix i.e. user*user and contains
    //the similarity score for every pair of users.
    private float user_user_matrix[][]; 


    public cfiltering()
    {
        //this is default constructor, which just creates the following:
        //ofcourse you need to overload the constructor so that it takes in the dimensions

        //this is 2d matrix of size 1*1
        user_movie_matrix=new int[1][1];
        //this is 2d matrix of size 1*1
        user_user_matrix=new float[1][1];
    }

    public cfiltering(int height, int width)
    {
        user_movie_matrix=new int[height][width];
        user_user_matrix=new float[height][height];
    }


    public static void main(String[] args) {
        //1.0 this is where you open/read file
        //2.0 read dimensions of number of users and number of movies
        //3.0 create a 2d matrix i.e. user_movie_matrix with the above dimensions. 
        //4.0 you are welcome to overload constructors i.e. create new ones. 
        //5.0 create a function called calculate_similarity_score 
        //you are free to define the signature of the function
        //The above function calculates similarity score for every pair of users
        //6.0 create a new function that prints out the contents of user_user_matrix 

        try
        {
            //fileinputstream just reads in raw bytes. 
            FileInputStream fstream = new FileInputStream("inputfile.txt");

            //because fstream is just bytes, and what we really need is characters, we need
            //to convert the bytes into characters. This is done by InputStreamReader. 
            BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
            int numberOfUsers=Integer.parseInt(br.readLine());
            int numberOfMovies=Integer.parseInt(br.readLine());

            //Now you have numberOfUsers and numberOfMovies to create your first object. 
            //this object will initialize the user_movie_matrix and user_user_matrix.

            new cfiltering(numberOfUsers, numberOfMovies);

            //this is a blankline being read
            br.readLine();
            String row;
            int userNo = 0;
            while ((row = br.readLine()) != null)   
            {
                //now lets read the matrix from the file
                String allRatings[]=row.split(" ");
                int movieNo = 0;
                for (String singleRating:allRatings)
                {
                    int rating=Integer.parseInt(singleRating);
                    //now you can start populating your user_movie_matrix
                    System.out.println(rating);
                    user_movie_matrix[userNo][movieNo]=rating;
                    ++ movieNo;
                }
                ++ userNo;
            }
        }
        catch(Exception e)
        {
            System.out.print(e.getMessage());
        }
    }

}

Answer 1

尝试关闭并重新打开该文件，然后按Ctrl+F11。

验证您运行的文件的名称是否与您正在使用的项目的名称相同，并且该文件中的公共类的名称与您正在使用的项目的名称相同同样。

否则，重启Eclipse。如果这解决了问题，请告诉我！否则，请发表评论，我会尽力帮助。

Answer 2

您是否为文件读取内容导入了包。

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;

也在这里

cfiltering(numberOfUsers, numberOfMovies);

您是在尝试创建对象还是调用方法？

另一件事：

user_movie_matrix[userNo][movieNo]=rating;

您正在为实例的成员分配值，就好像它是一个静态变量一样同时删除

中的Th

private int user_movie_matrix[][];Th

希望这有帮助。

Answer 3

private int user_movie_matrix[][];Th。应该是`private int user_movie_matrix[][];。

private int user_movie_matrix[][];应为private static int user_movie_matrix[][];

cfiltering(numberOfUsers, numberOfMovies);应为new cfiltering(numberOfUsers, numberOfMovies);

在这些更改之后代码是否按预期工作超出了本答案的范围;有几个语法/范围错误。

Eclipse错误：“编辑器不包含主类型”

3 个答案: