顺序读取文件时出现 NumberFormatException？

Question

本质上，该程序的目的是将学生信息写入文件并从同一文件中读取。该程序包含一个 if 语句，用于判断学生是否处于良好的信誉或学术试用期，每个文件都有各自的文件（goodstanding.txt 和 probation.txt）。如果我注释掉 goodstanding.txt 的读取逻辑，程序工作文件，但对我来说，除了文件路径之外，它们似乎几乎相同，显然。我查看了其他问题，但其中大多数似乎与错误的类型转换有关。它抛出的具体错误NumberFormatException For input string: ""在线ID = Integer.parseInt(array[0]);写逻辑如下：if(GPA >= 2.0) //If GPA >= 2.0, write to good standing file. This is                identical to probation writer, but causes an issue somewhere{     String result = ID + "," + fname + " " + lname + "," + GPA;     OutputStream out = new BufferedOutputStream(Files.newOutputStream(good,      StandardOpenOption.CREATE));     BufferedWriter wt = new BufferedWriter(new OutputStreamWriter(out));     wt.write(result, 0, result.length()); //Write to file from position 0 to                                         length     wt.newLine();     System.out.println("Please enter next WIN or 999 to quit: ");     ID = input.nextInt();     input.nextLine();     wt.close();}     if(GPA < 2.0) //If GPA < 2.0, write to probation file {     String result = ID + "," + fname + " " + lname + "," + GPA;     OutputStream out = new                    BufferedOutputStream(Files.newOutputStream(probation,                    StandardOpenOption.CREATE));     BufferedWriter wt = new BufferedWriter(new OutputStreamWriter(out));     wt.write(result, 0, result.length());     wt.newLine();     System.out.println("Please enter next WIN or 999 to quit: ");     ID = input.nextInt();     input.nextLine();     wt.close();}和读取逻辑：try{    while(line != null){    array = line.split(",");    ID = Integer.parseInt(array[0]);    name = array[1];    GPA = Double.parseDouble(array[2]);    double ahead = GPA - 2;    System.out.println("WIN: " + ID + " | " + " Name: " + name + " |" + " GPA                                         = " + GPA + " | Ahead by " + ahead);    line = reader.readLine(); }}我也尝试在 ID 上使用 trim() 方法，但异常仍然存在。是否有一个我需要阅读更多的概念来解释这一点？

Answer 1

我认为错误消息很清楚NumberFormatException For input string: ""，因为您无法将空字符串解析为int。

您的问题至少有两个原因，或者您的文件中有一些空白行，或者您的其中一行以逗号开头。通过执行以下操作来检查或忽略此类行：

....

    while (line != null) {

        if(!line.startsWith(",") && !line.isEmpty()){

            array = line.split(",");

            ID = Integer.parseInt(array[0]);

            name = array[1];

            GPA = Double.parseDouble(array[2]);

            double ahead = GPA - 2;

            System.out.println("WIN: " + ID + " | " + " Name: " + name + " |" + " GPA = " + GPA + " | Ahead by " + ahead);

        }

        line = reader.readLine();

    }