java - 在包含字符串和 double 的外部文本文件上使用扫描仪

Question

编写一个 java 程序来读取包含字符串和双倍价格表的文本文件，并将它们存储在 Hashmap 中。继续在 nextDouble() 行中收到“java.util.InputMismatchException”错误。代码:

    public static void main(String[] args) throws IOException {

        String priceList = "src/" + args[0];
        String cartOne = "src/" + args[1];
        String cartTwo = "src/" + args[2];
        Scanner priceScan = new Scanner(new File(priceList));
        priceScan.useDelimiter("    ");
        HashMap<String, Double> prices = new HashMap<String, Double>();
        priceScan.useDelimiter(" ");
        while (priceScan.hasNext()) {
            String name = priceScan.next();
            Double price = priceScan.nextDouble();
            prices.put(name, price);

        }
        priceScan.close();
        System.out.println(prices);
    }

文本文件如下:

TV          999.99
Table         199 
Bed         499.99
Chair         45.49
Milk    3.00
Butter  2.84
Tomato 0.76
Onion 0.54
Lettuce 1.00
Ham 2.50
Bread 1.75

Answer 1

您的映射将字符串映射到字符串，而它应该将字符串映射到 double 。

Scanner priceScan = new Scanner(new File(priceList));
HashMap<String, Double> prices = new HashMap<String, Double>();
while (priceScan.hasNext()) {
    String name = priceScan.next();
    Double price = priceScan.nextDouble();
    prices.put(name, price);
}
priceScan.close();