MVC Exercise

Let’s build a quick program following the MVC architecture style to review working with classes, object, inheritance, and polymorphism.

Problem Statement

Write a program to store a list of students and teachers at a school. The program should have methods to add a student or a teacher, as well as a method to print the entire list.

UML Diagram

The program should conform to the following UML diagram:

MVC Exercise UML Diagram MVC Exercise UML Diagram

Right-click and select “Open image in new tab” to view larger

The purpose of each method will be further described below.

Person Class

  • Person() - constructor that initializes all attributes based on parameters
  • getLastName() - getter for lastName attribute
  • getFirstName() - getter for firstName attribute
  • getAge() - getter for age attribute
  • happyBirthday() - method to increase person’s age attribute by $1$
  • toString() - method that overrides the built-in Object class toString() method. It should return a string in the form "firstName lastName: age"

Student Class

  • Student() - constructor that initializes all attributes (including in super class) based on parameters
  • getStudentID() - getter for studentID attribute
  • getGradeLevel() - getter for gradeLevel attribute
  • happyBirthday() - method to increase student’s age and gradeLevel attribute by $1$
  • toString() - method that overrides the built-in Object class toString() method. It should return a string in the form "firstName lastName: age (studentID - gradeLevel)"

Teacher Class

  • Teacher() - constructor that initializes all attributes (including in super class) based on parameters
  • getClassroom() - getter for classroom attribute
  • getSalary() - getter for salary attribute
  • happyBirthday() - method to increase teacher’s age by $1$ and salary attribute by $1000$
  • toString() - method that overrides the built-in Object class toString() method. It should return a string in the form "firstName lastName: age (classroom - $salary)"

View Class

  • showMenu() - a method to show a menu of options to the user. The user should be prompted to input exactly one of the options listed below, which is returned as a String. The wording of the menu is up to you. The method should return whatever was input by the user, without any error checking (that is done in the Controller)
    • “add student” - add a student
    • “add teacher” - add a teacher
    • “list people” - list the people
    • “exit” - exit the program
  • addStudent() - a method to add a new student to the system. The user should input a list of parameters for each attribute as they are listed in the constructor for Student, separated by spaces. The wording of the prompt is up to you. The method should return whatever was input by the user, without any error checking (that is done in the Controller)
    • Example: “Smith John 25 123456 13”
  • addTeacher() - a method to add a new teacher to the system. The user should input a list of parameters for each attribute as they are listed in the constructor for Teacher, separated by spaces. The wording of the prompt is up to you. The method should return whatever was input by the user, without any error checking (that is done in the Controller)
  • listPeople() - a method to list all Person objects in the persons array given as a parameter. Each one should be prefixed by an index starting at $0$, incrementing by one for each Person in the array. Remember that unused array slots will contain the value null so that should be considered in your code.
    • Example: “0) Smith John: 25 (geology - $1000)
  • showError() - a method to display an error to the user. The parameter error should be printed to the screen, prefixed by “Error: "

Controller Class

  • main() - the main method for this program. It should simply instantiate a new instance of the Controller class, and then call the run() method of that object.
  • Controller() - the constructor for the Controller object. It initialize the persons attribute to an array with a maximum size of 20 items, as well as a View object stored in the view attribute.
  • run() - this method consists of a loop that will execute the program until it is terminated. It will call the showMenu() method of the view to show a menu to the user (see above). Finally, it will parse the string returned by the call to showMenu() and call additional appropriate methods in the Controller or View class to complete the operation. If the user inputs “exit” then it should terminate. Otherwise, the program will repeatedly display the menu to the user until “exit” is chosen. If at any time the user provides input that cannot be properly parsed, the controller should call the showError() method in the View class and restart the process (loop back to the beginning) by showing the menu again.
  • addStudent() - this method will receive the string input by the user from the addStudent() method in View, parse the input, and call the appropriate methods to create a new Student object and add it to the first empty slot in the persons array.
  • addTeacher() - this method will receive the string input by the user from the addTeacher() method in View, parse the input, and call the appropriate methods to create a new Teacher object and add it to the first empty slot in the persons array.
  • getPersons() - this method will simply return the current persons attribute as an array. This is for testing purposes only
  • setPersons() - this method will replace the persons attribute with the array provided as a parameter. This is for testing purposes only.

Sample Execution

A sample execution of the program is shown below.

Sample Program Execution Sample Program Execution

Grading

Structure

{Check It!|assessment}(test-3269626908)

{Check It!|assessment}(test-2757569305)

{Check It!|assessment}(test-2923816668)

{Check It!|assessment}(test-3356253417)

{Check It!|assessment}(test-2664871931)

Functionality

{Check It!|assessment}(test-3442438399)

{Check It!|assessment}(test-163667115)

{Check It!|assessment}(test-496994260)

{Check It!|assessment}(test-2263639856)

{Check It!|assessment}(test-2809305019)

Info

Person

public class Person{
    private String lastName;
    private String firstName;
    private int age;
    
    public Person(String lastName, String firstName, int age){
        this.lastName = lastName;
        this.firstName = firstName;
        this.age = age;
    }
    
    public String getLastName(){ return this.lastName; }
    public String getFirstName(){ return this.firstName; }
    public int getAge(){ return this.age; }
    
    public void happyBirthday(){
        this.age = this.age + 1;
    }
    
    @Override
    public String toString(){
        return this.firstName + " " + this.lastName + ": " + this.age;
    }
}

Student

public class Student extends Person{
    private int studentID;
    private int gradeLevel;
    
    public Student(String lastName, String firstName, int age, int studentID, int gradeLevel){
        super(lastName, firstName, age);
        this.studentID = studentID;
        this.gradeLevel = gradeLevel;
    }
    
    public int getStudentID(){ return this.studentID; }
    public int getGradeLevel(){ return this.gradeLevel; }
    
    @Override
    public void happyBirthday(){
        super.happyBirthday();
        this.gradeLevel = this.gradeLevel + 1;
    }
    
    @Override
    public String toString(){
        return super.toString() + " (" + this.studentID + " - " + this.gradeLevel + ")";
    }
}

Teacher

public class Teacher extends Person{
    private String classroom;
    private int salary;
    
    public Teacher(String lastName, String firstName, int age, String classroom, int salary){
        super(lastName, firstName, age);
        this.classroom = classroom;
        this.salary = salary;
    }
    
    public String getClassroom(){ return this.classroom; }
    public int getSalary(){ return this.salary; }
    
    @Override
    public String toString(){
        return super.toString() + " (" + this.classroom + " - $" + this.salary + ")";
    }
}

View

import java.util.Scanner;

public class View{
    
    public String showMenu(){
        System.out.println("Please enter one of the following options:");
        System.out.println("  add student");
        System.out.println("  add teacher");
        System.out.println("  list people");
        System.out.println("  exit");
        try{
            Scanner scanner = new Scanner(System.in);
            String input = scanner.nextLine();
            return input;
        }catch(Exception e){
            return "";
        }
    }
    
    public String addStudent(){
        System.out.println("Please enter the following items for the new student, all on the same line");
        System.out.println("LastName FirstName Age StudentID GradeLevel");
        try{
            Scanner scanner = new Scanner(System.in);
            String input = scanner.nextLine();
            return input;
        }catch(Exception e){
            return "";
        }
    }
    
    public String addTeacher(){
        System.out.println("Please enter the following items for the new teacher, all on the same line");
        System.out.println("LastName FirstName Age Classroom Salary");
        try{
            Scanner scanner = new Scanner(System.in);
            String input = scanner.nextLine();
            return input;
        }catch(Exception e){
            return "";
        }
    }
    
    public void listPeople(Person[] persons){
        System.out.println("The school contains the following people:");
        int i = 0;
        for(Person p : persons){
            if(p == null){
                continue;
            }
            System.out.println(i + ") " + p.toString());
            i++;
        }
    }
    
    public void showError(String error){
        System.out.println("Error: " + error);
    }
}

Controller

public class Controller{
    
    private Person[] persons;
    private View view;
    private int size;
    
    public static void main(String[] args){
        new Controller().run(); 
    }
    
    public Controller(){
        this.persons = new Person[20];
        this.view = new View();
        this.size = 0;
    }
    
    public void run(){
       while(true){
            String input = view.showMenu();
            if(input.equals("add student")){
                addStudent(view.addStudent());
            }else if(input.equals("add teacher")){
                addTeacher(view.addTeacher());
            }else if(input.equals("list people")){
                view.listPeople(persons);
            }else if(input.equals("exit")){
                break;
            }else{
                view.showError("Invalid Input!");
            }
        } 
    }
    
    public void addStudent(String input){
        String[] splits = input.split(" ");
        try{
            Person p = new Student(splits[0], splits[1], Integer.parseInt(splits[2]), Integer.parseInt(splits[3]), Integer.parseInt(splits[4]));
            if(size < 20){
                persons[size++] = p;
            }else{
                view.showError("Array full!");
            }
        }catch(Exception e){
            view.showError("Unable to parse input!");
        }
    }
    
    public void addTeacher(String input){
        String[] splits = input.split(" ");
        try{
            Person p = new Teacher(splits[0], splits[1], Integer.parseInt(splits[2]), splits[3], Integer.parseInt(splits[4]));
            if(size < 20){
                persons[size++] = p;
            }else{
                view.showError("Array full!");
            }
        }catch(Exception e){
            view.showError("Unable to parse input!");
        }
    }
    
    public Person[] getPersons() { return persons; }
    public void setPersons(Person[] input) { persons = input; }
}

5.18.0

Last modified by: Russell Feldhausen Aug 17, 2021