Question

我目前有以下代码将数据从txt文件读取到对象。但是ArrayList无法正常工作。

public static void load_Recipes() {
    // Read file and load data into ingredient object
    String[] current_line = new String[7];

    // Variables for the ingredient object attributes
    int recipeID;
    String recipeName;
    int recipePrepTime;
    String recipeURL;
    String recipeCuisine;
    String recipeType;
    double recipeRating;
    String recipeIngredients;
    ArrayList<Integer> recipeContainsID = new ArrayList<Integer>();
    //String cleanString[] = new String[20];
    //ArrayList<String> stringInt = new ArrayList<String>();


    try {
        int i = 0;
        BufferedReader my_reader = new BufferedReader(new FileReader("recipes.txt"));
        String input_line; //variable to read line by line
        while( (input_line=my_reader.readLine()) != null){
            current_line = input_line.split("\t"); //split the line at the tab
            recipeID = Integer.parseInt(current_line[0]);
            recipeName = current_line[1];
            recipePrepTime = Integer.parseInt(current_line[2]); 
            recipeURL = current_line[3];
            recipeCuisine = current_line[4];
            recipeType = current_line[5];
            recipeRating = Double.parseDouble(current_line[6]); 
            recipeIngredients = current_line[7];
            System.out.println("The current value of recipeIngredients is: " + recipeIngredients); // Checking current value, removed when working
            String clean1[] = recipeIngredients.replaceAll("\\[|\\]|","").split(",");

            for(int j = 0; j < clean1.length; j++) {
                System.out.print(clean1[j] + ", "); // Checking the current value, removed when working
                recipeContainsID.add(Integer.parseInt(clean1[j]));
            }

            // test
            all_recipes[i] = new Recipe(recipeID, recipeName, recipePrepTime, recipeURL, recipeCuisine, recipeType, recipeRating, recipeContainsID);
            System.out.println("Next object.");
            i++;
        }
        my_reader.close();
    }
    catch(IOException e){
        System.out.println("can't read file");
    }
}

文本文件包含以下内容：

1   Spaghetti   60  wwww.cooking.nl italiaans   tussengerecht   1.0 [1,2,3,4]
2   Lasagna 30  wwww.cooking.nl italiaans   tussengerecht   3.2 [5,6,7,8]
3   Groente 40  wwww.cooking.nl italiaans   hoofdgerecht    3.1 [7,3,8,4]
4   Risotto 90  wwww.cooking.nl italiaans   hoofdgerecht    4.1 [3,2,5,4]

每当我尝试将[]之间的最后一个整数写入对象ArrayList时，它们都会被添加到1个列表中。控制台中的输出：

1   Spaghetti   60  wwww.cooking.nl itialiaans  tussengerecht   1.0 [1, 2, 3, 4, 5, 6, 7, 8, 7, 3, 8, 4, 3, 2, 5, 4]
2   Lasagna 30  wwww.cooking.nl itialiaans  tussengerecht   3.2 [1, 2, 3, 4, 5, 6, 7, 8, 7, 3, 8, 4, 3, 2, 5, 4]
3   Groente 40  wwww.cooking.nl itialiaans  hoofdgerecht    3.1 [1, 2, 3, 4, 5, 6, 7, 8, 7, 3, 8, 4, 3, 2, 5, 4]
4   Risotto 90  wwww.cooking.nl itialiaans  hoofdgerecht    4.1 [1, 2, 3, 4, 5, 6, 7, 8, 7, 3, 8, 4, 3, 2, 5, 4]

打印代码：

public static void view_Recipes() {
    for(int i=0;i<Recipe.getNum_recipes();i++)
        System.out.println(all_recipes[i].getRecipeID() + "\t" + all_recipes[i].getRecipeName() + "\t" + all_recipes[i].getRecipePrepTime() + "\t" + all_recipes[i].getRecipeURL() + "\t" + all_recipes[i].getRecipeCuisine() + "\t" + all_recipes[i].getRecipeType() + "\t" + all_recipes[i].getRecipeRating() + "\t" + all_recipes[i].getRecipeContainsID());
}

Answer 1

您需要在处理下一行配方之前声明arraylist，即在while循环内部。否则，相同的arraylist会不断累积，因为它是同一个对象，它将为每一行包含相同的值。

移动此行

循环中的

ArrayList<Integer> recipeContainsID = new ArrayList<Integer>();。

while( (input_line=my_reader.readLine()) != null) { ArrayList<Integer> recipeContainsID = new ArrayList<Integer>(); .... ... ...

Answer 2

这是因为您的import numpy as np from scipy import sparse import matplotlib matplotlib.use('pdf') import matplotlib.pyplot as plt import networkx as nx if __name__=='__main__': hour_dense = np.zeros((986, 986)) hour_dense[80, 409] = 1 hour_dense[80, 891] = 1 hour_1 = sparse.csr_matrix(hour_dense) edges = nx.from_scipy_sparse_matrix(hour_1) options = { 'node_color': 'black', 'node_size': 3, 'line_color': 'red', 'linewidths': 1, 'edge_color':'red', 'width': 0.1, } nx.draw(edges, **options) plt.savefig('train_graph_hour_1.png') ArrayList不在循环迭代中。

receipeContainsID

在读取每一行时将其移动到循环中，你应该没问题。

Answer 3

你可以创建一个2维ArrayList<ArrayList<Integer>> recipeContainsID并为每个食谱保留一个列表，你将它们全部添加到同一个ArrayList中......你必须小心为每个新配方初始化一个新的ArrayList。

Answer 4

你应该注意while循环中的赋值。除recipeContainsID之外的每个变量都会在那里更新。对于基元，您要分配新值，而对于String对象，您要为新创建的实例分配引用（请注意，字符串是不可变的）。

因此，如果要将值添加到单独的列表中，则需要为每个已处理的行创建新列表。如果您不想对这些列表进行任何更改，可以使用Arrays.asList()方法创建它们。

recipeContainsID = Arrays.asList(clean1);

将文件读取到ArrayList和Object

4 个答案: