Question

我目前正在尝试创建一个小程序，将食谱创建为csv文件。直到我想要添加一个在中间带有空格的“成分”为止，效果都很好：“真正的大香蕉”。每当我写这样的东西，带下划线或带负号的东西时，它都会输入null而不是我写的单词。我有一个类的成分（双量，字符串单位，字符串成分，字符串标签）与所有变量的getter和setters。我创建csv的代码

public static ArrayList<Ingredients> createIngredientList() {

    Scanner scan =  new Scanner(System.in);
    ArrayList<Ingredients> list = new ArrayList<Ingredients>();
    char quit = 'Y';
    String unit, ingredient, tags;
    double amount;

    while(quit == 'Y') {
        System.out.print("Please use underscores instead of spaces e.g. real_big_boats.\n");
        System.out.print("Amount: ");
        amount = scan.nextDouble();

        System.out.print("Unit: ");
        unit = scan.next();

        System.out.print("Ingredient: ");
        ingredient = scan.nextLine();

        System.out.print("Tags (e.g. tag;tag;tag): ");
        tags = scan.nextLine();

        list.add(new Ingredients(amount, unit, ingredient, tags));

        System.out.print("More Ingredients? (Y/N) ");
        String s = scan.next();
        s = s.toUpperCase();
        quit = s.charAt(0);

    }

    return list;

}

您可以在下面的我的pastebin中找到整个课程。 https://pastebin.com/vi09kGqi

Answer 1

    while (quit == 'Y') {

        System.out.print("Please use underscores instead of spaces e.g. real_big_boats.\n");
        System.out.print("Amount: ");
        amount = scan.nextDouble();
        scan.nextLine() ;

        System.out.print("Unit: ");
        unit = scan.next();
        scan.nextLine() ;

        System.out.print("Ingredient: ");
        ingredient = scan.findInLine("(\\s|\\S)*");
        scan.nextLine() ;

        System.out.print("Tags (e.g. tag;tag;tag): ");
        tags = scan.next();
        scan.nextLine() ;

        list.add(new Ingredients(amount, unit, ingredient, tags));

        System.out.print("More Ingredients? (Y/N) ");
        String s = scan.next();
        scan.nextLine() ;
        s = s.toUpperCase();
        quit = s.charAt(0);
    }

Answer 2

这是由于Java中Scanner的一个已知问题。在此处查看链接：Scanner is skipping nextLine() after using next() or nextFoo()?

您可以在每个scanner.nextDouble（）或scanner.next（）之后使用空白的scanner.nextLine（）来解决此问题。

   public static ArrayList<Ingredients> createIngredientList() {

    Scanner scan =  new Scanner(System.in);
    ArrayList<Ingredients> list = new ArrayList<Ingredients>();
    char quit = 'Y';
    String unit, ingredient, tags;
    double amount;

    while(quit == 'Y') {
        System.out.print("Please use underscores instead of spaces e.g. real_big_boats.\n");
        System.out.print("Amount: ");
        amount = scan.nextDouble();
        scan.nextLine();

        System.out.print("Unit: ");
        unit = scan.next();
        scan.nextLine();

        System.out.print("Ingredient: ");
        ingredient = scan.nextLine();

        System.out.print("Tags (e.g. tag;tag;tag): ");
        tags = scan.nextLine();

        list.add(new Ingredients(amount, unit, ingredient, tags));

        System.out.print("More Ingredients? (Y/N) ");
        String s = scan.next();
        s = s.toUpperCase();
        quit = s.charAt(0);

    }

    return list;

}

输出：

Please use underscores instead of spaces e.g. real_big_boats.
Amount: 111
Unit: 111
Ingredient: a b c
Tags (e.g. tag;tag;tag): a b c
More Ingredients? (Y/N) N
Ingredients [amount=111.0, unit=111, ingredient=a b c, tags=a b c]

另一种解决方案是通过使用Scanner.nextLine（）将每个输入作为String接受，然后将其解析为所需的类型。

将多个单词写入一个CSV单元

2 个答案: