java - 尝试从文件中读取数据(文件每两行包含换行符)

Question

首先，这是数据文件的样子

5165168416516988798484984984984984
9898798798798

1556516846516518498
51688484979789798798798491

我需要阅读该换行符之前的两行(我可以做到)，然后继续两两阅读，直到文件结束。配对数量保证为偶数，因此最后不会出现孤行。我的问题是尝试读取前两行以外的文件。

code
try {
    Scanner input = new Scanner (file);
    while (input.hasNextLine()) {
        String number1 = input.nextLine();
        String number2 = input.nextLine();

        System.out.println("String: " + number1);
        System.out.println("String: " + number2);

        System.out.println(number1 + " " + number2);

        number1= input.nextLine();
        number2= input.nextLine();
    }
} 

是我到目前为止所做的。它仅在根本没有换行符的情况下才有效，但它仍然会在最后抛出一个异常(“找不到行”)。

一旦在文件中找到第一个中断，就会发生此异常。如何使整个文件以我想要的方式读取？ (捕获这两行，对它们做点什么。捕获接下来的两行，做点什么……一直到最后)

Answer 1

好的。让我们试试。

try {
    Scanner input = new Scanner (file);

    // input.hasNextLine() checks if there are more lines that can be read from
    // the file. If there is a line, hasNextLine() will return true, and the code
    // inside the while block will be executed.
    // Then execution will come back here to perform the check again. This
    // goes on until there are no more lines to consume.
    while (input.hasNextLine()) {

        // We are going to read two numbers from file.
        // Ideally, we should check if there a line available before reading
        // each of these lines. But since you confirm that the file will
        // always have multiple number of triplets containing two lines
        // with numbers, followed by a blank line, we are not going to
        // call input.hasNextLine() here.
        String number1 = input.nextLine();
        String number2 = input.nextLine();

        // Now, two numbers are read, read the next (empty) line to a variable
        // but we will not use it anywhere.
        String emptyLine = input.nextLine();
        // ...or we could read it, but just discard it without assigning it to a variable
        // input.nextLine();

        // Print what we read to the output, like a boss.
        System.out.println("String: " + number1);
        System.out.println("String: " + number2);
        System.out.println(number1 + " " + number2);

        // This is not needed here (see below to understand why):
        //number1= input.nextLine();
        //number2= input.nextLine();

        // after the following brace (}), execution will go back to the start
        // of the while loop. and if there are more lines to be read, code
        // inside while loop will be executed again.
    }
}

希望这能解决问题。

警告:要使此代码无误运行，您的输入文件中最后一个数字对后必须包含一个空行。否则它会抛出一个 NoSuchElementException。