Question

所以我有这个代码，它应该从一个名为“Numbers.txt”的文件中读取数据。在这个文件中，它只是2003行十进制数。该程序的目标是读取此文件并进行计算。首先，我必须得到平均值，这是我设法做到的，但问题是我现在必须重新进入并获得标准偏差。它编译得很好，但我得到一个运行错误如下：

Exception in thread "main" java.lang.IllegalStateException: Scanner closed
    at java.util.Scanner.ensureOpen(Scanner.java:1115)
    at java.util.Scanner.hasNext(Scanner.java:1379)
    at StatsDemo.main(StatsDemo.java:49)

这是我的代码：

File rf2 = new File("Numbers.txt"); //reconnect to the FileReader object passing it the filename
    Scanner inputFile2 = new Scanner(rf2);//reconnect to the BufferedReader object passing it the FileReader object.
    sum = 0; //reinitialize the sum of the numbers
    count = 0; //reinitialize the number of numbers added
    //priming read to read the first line of the file
    while (inputFile.hasNext()) //loop that continues until you are at the end of the file
    {
     difference = inputFile.nextDouble() - mean; //convert the line into a double value and subtract the mean
        sum += Math.pow(difference,2); //add the square of the difference to the sum
        count++; //increment the counter
        if (inputFile.hasNextDouble())
        inputFile.nextLine(); //read a new line from the file
    }
  inputFile.close(); //close the input file
    stdDev = Math.sqrt(sum/count); //store the calculated standard deviation

我不知道为什么我会收到这个错误。我从之前的平均计算中得到了一个类似的（但不是相同的），但对此的解决方案并不适用。有什么想法吗？

更改为inputFile2 ...

Exception in thread "main" java.lang.IllegalStateException: Scanner closed
at java.util.Scanner.ensureOpen(Scanner.java:1115)
at java.util.Scanner.next(Scanner.java:1510)
at java.util.Scanner.nextDouble(Scanner.java:2456)
at StatsDemo.main(StatsDemo.java:51)

Answer 1

将inputFile替换为inputFile2，因为它是Scanner对象。

Answer 2

您的Scanner被称为inputFile2而不是inputFile。

Answer 3

在代码inputFile

中将inputFile2重命名为while (inputFile.hasNext())

Answer 4

您的Scanner对象使用inputFile2，并且您使用inputFile作为扫描仪对象。我很惊讶您的代码是如何运行的，没有任何编译错误。如果您有另一个与inputFile Scanner对象相关联的文件，但您没有提供上面的代码，只需检查文件并关闭您正在刷新inputFile对象的那个引用。否则，请更正以下代码：

File rf2 = new File("Numbers.txt"); //reconnect to the FileReader object passing it the filename
    Scanner inputFile2 = new Scanner(rf2);//reconnect to the BufferedReader object passing it the FileReader object.
    sum = 0; //reinitialize the sum of the numbers
    count = 0; //reinitialize the number of numbers added
    //priming read to read the first line of the file
    while (inputFile2.hasNext()) //loop that continues until you are at the end of the file
    {
     difference = inputFile2.nextDouble() - mean; //convert the line into a double value and subtract the mean
        sum += Math.pow(difference,2); //add the square of the difference to the sum
        count++; //increment the counter
        if (inputFile2.hasNextDouble())
        inputFile2.nextLine(); //read a new line from the file
    }
  inputFile2.close(); //close the input file
    stdDev = Math.sqrt(sum/count); //store the calculated standard deviation

在Java中运行错误...扫描仪已关闭？

4 个答案: