Question

我继续将阵列排除在外，因为学生可以有不同的成绩，因此如果学生没有3年级，但另一个学生没有，我的程序会自动崩溃。我该怎么做才能使该计划根据学生的不同分数。

public class StudentList  extends Component{

static  ArrayList<Student> studentList = new ArrayList<>();
public  static final int ARRAYMAX=4;

public void readStudent()throws Exception{

    File window = new File(System.getProperty("user.home"));
    JFileChooser choice = new JFileChooser();
    choice.setCurrentDirectory(window);
    int option = choice.showOpenDialog(this);
    File selectedFile = choice.getSelectedFile();
    if (option == JFileChooser.APPROVE_OPTION) {
        System.out.println("Selected file: " + selectedFile.getAbsolutePath());
    }
    File studentFile = new File(selectedFile.getAbsolutePath());

    Scanner in = new Scanner(studentFile);

     while (in.hasNext()) {
         String data = in.nextLine();

            String[] studentData = new String[ARRAYMAX];
            studentData = data.split("\\|");

                for(int i =0; i<ARRAYMAX; i++){
                    studentData[i] ="0";
               }

        String firstName = studentData[0];
        String lastName  = studentData[1];

        double grade1 = Double.parseDouble(studentData[2]);
        double grade2 = Double.parseDouble(studentData[3]);

        double grade3 = Double.parseDouble(studentData[4]);

        Student newStudent = new Student(firstName,lastName);
        newStudent.setGrades1(grade1);
        newStudent.setGrades2(grade2);
        newStudent.setGrades3(grade3);
     }

  }

}

Answer 1

默认等级（等级1，等级2等）到合理值。在访问studentData并设置成绩之前检查studentData的长度（studentData.length）。

另一方面，为什么要使用个别grade字段/ setter？只需将所有等级存储在List或Array字段中，然后根据您的需要访问它。

Answer 2

好吧，如果我理解正确的话，有些线路没有三年级。如果是这样，您可以检查它是否具有3年级public class StudentList extends Component{ static ArrayList<Student> studentList = new ArrayList<>(); public static final int ARRAYMAX=4; public void readStudent()throws Exception{ File window = new File(System.getProperty("user.home")); JFileChooser choice = new JFileChooser(); choice.setCurrentDirectory(window); int option = choice.showOpenDialog(this); File selectedFile = choice.getSelectedFile(); if (option == JFileChooser.APPROVE_OPTION) { System.out.println("Selected file: " + selectedFile.getAbsolutePath()); } File studentFile = new File(selectedFile.getAbsolutePath()); Scanner in = new Scanner(studentFile); while (in.hasNext()) { String data = in.nextLine(); String[] studentData = new String[ARRAYMAX]; studentData = data.split("\\|"); for(int i =0; i<ARRAYMAX; i++){ studentData[i] ="0"; } String firstName = studentData[0]; String lastName = studentData[1]; double grade1 = Double.parseDouble(studentData[2]==null?"0":studentData[2]); double grade2 = Double.parseDouble(studentData[3]==null?"0":studentData[3]); double grade3 = Double.parseDouble(studentData[4]==null?"0":studentData[4] ); Student newStudent = new Student(firstName,lastName); newStudent.setGrades1(grade1); newStudent.setGrades2(grade2); newStudent.setGrades3(grade3); } }

使用jfilechooser为java将文本文件放入数组中

2 个答案: