java - 如何使用 while 循环用不同类型的对象填充数组列表

Question

   public void importStudent(String fileName) throws FileNotFoundException{
        File input = new File("students.txt");
        Scanner readFile = new Scanner(input);
        ArrayList<Object> tokensList = new ArrayList<Object>();

        while (readFile.hasNextLine()){

            tokensList.add(readFile.nextLine().split(","));

            String FirstName = (String) tokensList.get(0);
            String LastName = (String) tokensList.get(1);
            String phoneNum = (String) tokensList.get(2);
            String address = (String) tokensList.get(3);
            double gpa = (double) tokensList.get(4);
            String major = (String) tokensList.get(5);
            double creditsTaking = (double) tokensList.get(6);
            //all of the stuff in one line of the text file
            Student s = new Student( FirstName, LastName, phoneNum, address, gpa,
                    major, creditsTaking);
            peopleBag.add(s);
        }
        readFile.close();
    }

所以我有一个文本文件，其中每一行都包含我尝试创建的 Student 类的一个对象的所有信息。我想要做的是读取文本文件的一行，将信息添加到数组列表中，然后使用该列表来满足我的 Student 构造函数的所有字段。该方法没有红线，但运行该方法时出现以下错误:

Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.lang.String at step1.PeopleBag.importStudent(PeopleBag.java:35) at step1.Demo.main(Demo.java:10)

Answer 1

String.split 返回一个数组，而不是 List。你可以像这样修复它，

List<String> tokensList = new ArrayList<>();
tokensList.add(Arrays.asList(readFile.nextLine().split(",")));

或者将tokensList更改为数组，然后像数组一样访问它。

String[] tokens = readFile.nextLine().split(",");
String FirstName = tokens[0];
// ...