Question

我可以从用户那里获得scan2扫描仪的输入。但是在这段代码中没有生成扫描，我怎么能进入这个循环我无法从用户那里获得扫描扫描仪的输入。如何从用户那里获得扫描扫描仪的输入。

    Scanner scan2 = new Scanner(System.in);
    System.out.println("Register Section\nID: ");
    String id = scan2.next();
    System.out.println("Password: ");
    String pass = scan2.next();
    createAccount(id, pass, accounts);
    System.out.println("Login Section\nID: ");
    id = scan2.next();
    System.out.println("Password: ");
    pass = scan2.next();
    boolean X = logIN(id, pass, students);  
    scan2.close();

//Login succeed

    if(X){

    Scanner scan = new Scanner(System.in);
    String line = "";

    while (scan.hasNextLine()) {    
        line = scan.nextLine();
        if (line.equalsIgnoreCase("quit"))
            System.exit(0);

        int timetablestart = line.indexOf('[');
        int timetablefinish = line.indexOf(']');

        String strlistoftimetable = "";
        String command = line;
        String[] timetableslots = null;
        if ((timetablestart > 0) && (timetablefinish > 0)) {
            strlistoftimetable = line.substring(timetablestart + 1,
                    timetablefinish);
            timetableslots = strlistoftimetable.split(", ");
            command = line.substring(0, timetablestart - 1);
        }

        String[] tokens = command.split("\\s");
        if (tokens.length < 2) {
            System.out.println("something is wrong!");
            return;
        }



        if (tokens[0].equals("add")) {
            if (tokens[1].equals("O")) {

                CSDriver.addO(tokens,timetableslots,departments);


            } else if (tokens[1].equals("C")) {

                CSDriver.addC(tokens, students);

            } else if (tokens[1].equals("I")) {

                CSDriver.addI(tokens,instructors);


            } 

        }

        else if (tokens[0].equals("print")) {

            if (tokens[1].equals("S")) {

                CSDriver.printS(tokens, students);


            } else if (tokens[1].equals("I")) {

                CSDriver.printI(tokens,instructors);

            }
              else if (tokens[1].equals("Announcement")) {

                CSDriver.printAnnouncement(departments);

            }
             else if (tokens[1].equals("AcedemicActivities")) {

CSDriver.printAcedemicActivities(departments);}
             else if (tokens[1].equals("Attendance")) {

                    CSDriver.checkAttendance(tokens, students);

                }
             else if (tokens[1].equals("Internship")) {

                CSDriver.checkInternship(tokens, students);

            }

             else if (tokens[1].equals("SemesterGrades")) {

                CSDriver.checkSemesterGrades(tokens, students);
            }
        }           else 
            System.out.println("something is wrong!");


    }

    scan.close();
}   }

Answer 1

您没有从scan获得任何内容，因为您已经关闭System.in（在关闭scan2时，在“登录成功”部分结束时）。您不应该自己关闭它，因为它会阻止将来尝试从此流中读取。

Answer 2

使用时

Scanner scan2 = new Scanner(System.in);
scan2.close();

您正在关闭 scan2 ，但 System.in ，因此为了解决您的问题，您需要在程序结束时关闭扫描仪。

在最后移动此行

scan2.close();

Java从用户那里获得输入

2 个答案: