Abstract Classes.

[maknib]

Hey guys.

for my assignment i must use an abstract class called User.
i also have admin and instructor classes which extend User.

i have a User array which is storing all my objects either admin or instructor objects and IF they are instructors they have courses.
i want to print out the courses so i tried

if(userArray[i].getRole().equals("instructor")){
            System.out.println("courses: "+ userArray[i]);
         }

but eclipse is telling me that this method doesn't exist for class User.
in class User i have

public abstract class User {
   public String username;
   public String password;
   
   public abstract String getUsername();
   public abstract String getPassword();
   public abstract String getRole();
   
   
}

i didnt put a method in there as admins don't have courses.

should i still be defining a method in the abstract class for courses?

or am i doing this completely wrong?

thanks

[dlorde]

i want to print out the courses so i tried

if(userArray[i].getRole().equals("instructor")){
            System.out.println("courses: "+ userArray[i]);
         }

That code tries to print out the user (if it's an instructor). I don't see any courses in your code at all.

eclipse is telling me that this method doesn't exist for class User.

Which method? Post up the full error message text.

i didnt put a method in there as admins don't have courses.

What method?

should i still be defining a method in the abstract class for courses?
or am i doing this completely wrong?

I don't know, the only place in your code that courses are mentioned is in a text string that is printed.

Perhaps if you explained clearly and concisely what it is you're trying to achieve, it might become clearer.

Incidentally, to save a lot of confusion, please use the Java naming conventions - class names start with an UPPERCASE letter, variable and method names start with a lowercase letter.

[maknib]

That code tries to print out the user (if it's an instructor). I don't see any courses in your code at all.

Which method? Post up the full error message text.

What method?



I don't know, the only place in your code that courses are mentioned is in a text string that is printed.

Perhaps if you explained clearly and concisely what it is you're trying to achieve, it might become clearer.

Incidentally, to save a lot of confusion, please use the Java naming conventions - class names start with an UPPERCASE letter, variable and method names start with a lowercase letter.

Sorry.. all classes are below.

im reading a txt file of users. i have to determine if they are instructors or admins and create objects of them.

i am trying to print out the courses property on given to instructors but i get

xception in thread "main" java.lang.Error: Unresolved compilation problem:
The method getCourses() is undefined for the type User

at RequestApp.main(RequestApp.java:27)

i didn't make one in the abstract User class because admin doesn't use courses. so now i'm wondering if i have done this completely wrong :confused:



User class

public abstract class User {
   public String username;
   public String password;
   
   public abstract String getUsername();
   public abstract String getPassword();
   public abstract String getRole();
   
}

Instructor class

public class Instructor extends User {
   
   private String courses;
   private String role = "instructor";
      
   Instructor(String line) {

      String[] userDetails = line.split("\\s+\\|\\s+");

      if (userDetails.length == 4) {
         username = userDetails[0];
         password = userDetails[1];
         courses = userDetails[3];
      } else if (userDetails.length == 3) {
         username = userDetails[0];
         password = userDetails[1];
         courses = "none";
      }
      
      
   }
   
   public String getUsername(){
      return username;
   }
   
   public String getPassword(){
      return password;
   }
   
   public String getRole(){
      return role;
   }
   
   public String getCourses(){
      return this.courses;
   }
}

Admin class

public class Admin extends User {
   
   private String role = "admin";
     

   Admin(String line) {

      String[] userDetails = line.split("\\s+\\|\\s+");
      
      username = userDetails[0];
      password = userDetails[1];
   }
   
   public String getUsername(){
      return username;
   }
   
   public String getPassword(){
      return password;
   }
   
   public String getRole(){
      return role;
   }
}

Main..

mport java.io.*;

public class RequestApp {

   private static String[] users;
   private static String[] requests;
   private static User[] userArray;

   public static void main(String[] args) throws IOException {
      // read login text file and create user objects

      try {
         ReadFile file = new ReadFile();
       userArray = file.openFile("login.txt");

      }

      catch (IOException e) {
         System.out.println(e.getMessage());
      }
      
      for(int i = 0; i < userArray.length; i++){
         System.out.println("username: " + userArray[i].getUsername());
         System.out.println("password: " + userArray[i].getPassword());
         System.out.println("role: " + userArray[i].getRole());
         if(userArray[i].getRole().equals("instructor")){
            System.out.println("courses: "+ userArray[i].getCourses());
         }
         System.out.println();
      }

[Tolls]

Can I suggest overriding the toString() method in your User and Instructor classes?
The User toString() will build a String containing the username/password/role.
The Instructor class will call the User toString (super.toString()) and append the course data to it.

Your printout code will then simply loop round the user list calling System.out.println(userArray[i].toString()).