Method calling within the same method

Question

I am working on a small app that will allow a student to join a class when selected. I want to have the user be able to select a student by ID, select a class by ID and have the user be added to that class. This works, but after the student is added, I want the program to ask if the student wants to join another class, instead of resetting the whole program and having to go back.

I think I am close to a solution, but do not know how to get my method (signUp()) to go back to halfway through the method. Does this make sense? Once a student is entered in a class and "join another class" is selected I want to return to the bold comment in the code.

Sorry if this is long-winded and confusing, I'm new to this, so I appreciate your patience!

static void signUp() {
        System.out.println("\nSign Up For a Class\n");
        try {
          Scanner input = new Scanner(System.in);
          System.out.println("Enter Student ID: ");
          String user_entered_student_id = input.nextLine();

          Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/ClassSelector?autoReconnect=true&useSSL=false", "", "");
          Statement myStmt = con.createStatement();
          Statement myStmt2 = con.createStatement();
          Statement myStmt3 = con.createStatement();

          ResultSet rs;
          rs = myStmt.executeQuery("SELECT student_name FROM ClassSelector.students WHERE student_id = " + user_entered_student_id);
          while (rs.next()) {
            String userEnterId = rs.getString("student_name");
            System.out.println("Is " + userEnterId + " the correct student? (Y/N)");
            String confirm = input.nextLine();

            if (confirm.equals("Y") || confirm.equals("y")) {
              ResultSet rs2 = myStmt2.executeQuery("SELECT * FROM ClassSelector.classes");
              while (rs2.next()) {
                String avlClasses = rs2.getString("class_id") + "\t" + rs2.getString("classname") + "\t" + rs2.getString("description");
                System.out.println(avlClasses);
              }
            } else if (confirm.equals("N") || confirm.equals("n")) {
              System.out.println("Oops, let start over");
              return;
            }
    **//RETURN TO THIS SECTION OF CODE AND PROCEEED**
            System.out.println("Enter Class ID from Classes Listed Above to Join: ");
            String selectedClass = input.nextLine();
            ResultSet rs3 = myStmt3.executeQuery("SELECT * FROM ClassSelector.classes WHERE class_id = " + selectedClass);
            while (rs3.next()) {
              String innerJoin = (userEnterId + " has been added to " + rs3.getString("classname") + " " + rs3.getString("class_id"));
              System.out.println(innerJoin);
              String student_classJoin = "INSERT IGNORE INTO student_x_class" + "(student_id,student_name, class_id, classname)" + "VALUES (?, ?, ?, ?)";
              PreparedStatement pStmt = con.prepareStatement(student_classJoin);
              pStmt.setString(1, user_entered_student_id);
              pStmt.setString(2, userEnterId);
              pStmt.setString(3, rs3.getString("class_id"));
              pStmt.setString(4, rs3.getString("classname"));
              pStmt.executeUpdate();
              System.out.println("Would you like to enroll " + userEnterId + " into another class? (Y/N)");
              String additionalClass = input.nextLine();
              if(additionalClass.equals("Y") || additionalClass.equals("y")){
                  signUp();
              }
            }
          }
        } catch (java.sql.SQLException SQL) {
          SQL.printStackTrace();
        } catch (Exception EXC) {
          EXC.printStackTrace();
        }

      }

Answer 1

This code is very confusing. But let's take a step back and look at some pseudo -code which may represent the sort of structure you're looking for.

Let's start with the operation being performed. Something like this:

studentID = prompt("enter a student ID");
student = get_from_data(studentID);
courseID = prompt("enter a course ID");
course = get_from_data(courseID);
insert_in_data(studentID, courseID);

The details are very implementation-specific, but in general your primary logical approach should semantically look very similar to that. In fact, it's often a very good idea to extract code into small individual methods where the method name describes the operation being performed. Then the overall sequence of steps reads like a short story which describes the business process.

Now, you want to repeat that structure? Well, that's what loops are for. Something like this:

while(!someTerminatingCondition) {
    // the steps above
}

Now we just need to define that condition. It's based on user input, right? So something like this:

shouldContinue = true;
while(shouldContinue) {
    // the steps above
    shouldContinue = prompt("continue?");
}

To give you something to Google, what you're describing is often called a "game loop". The idea is that the entire process should repeat, over and over, until some specific condition is met. (In a game this condition would be the determination of a winner.)