java - 扫描仪在输入文件的末尾处失败

Question

我有以下代码:

    Scanner in = new Scanner(new FileReader("in.txt"));

    while(in.hasNext()){
        System.out.println(in.nextLine());
        System.out.println(in.nextLine());
        System.out.println(in.nextDouble());
        System.out.println(in.nextDouble());
        System.out.println(in.nextDouble());

        System.out.println(in.nextLine());
    }

其中 in.txt 的格式为:

One Name
Second Name
double
double
double
One Name
Second Name
double
double
double
...

但是，while 循环在输入文件的最后一行失败。它打印整个输入文件，但是完成后我收到一条错误消息:

Exception in thread "main" java.util.NoSuchElementException: No line found
    at java.util.Scanner.nextLine(Scanner.java:1585)
    at start.Start.main(Start.java:22)
Java Result: 1

Answer 1

每次读取之前都必须调用hasNext()方法，因为如果为true，该方法可以保证至少还有一个元素要读取。您的阅读内容应如下所示:

    if (in.hasNext())
        System.out.println(in.nextLine());
    if (in.hasNext())
        System.out.println(in.nextLine());
    if (in.hasNext())
        System.out.println(in.nextDouble());
    if (in.hasNext())
        System.out.println(in.nextDouble());
    if (in.hasNext())
        System.out.println(in.nextDouble());

    if (in.hasNext())
        System.out.println(in.nextLine());