what is the solution for this Java problem? Generics Suppose you need to process the following...

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what is the solution for this Java problem?

Generics Suppose you need to process the following information regarding Students and Courses: A Student has a name, age, ID,

what is the solution for this Java problem? Generics Suppose you need to process the following...

Generics Suppose you need to process the following information regarding Students and Courses: A Student has a name, age, ID, and courseList. The class should have a constructor with inputs for setting name, ID and age. The class should have setters and getters for attributes name, ID and age, and a method addCourse, removeCourse, printSchedule. courseList: use the generic class ArrayList<E> as the type of this attribute addCourse: this method takes as input a course. If the course is already in the list return false. Else, add the course to the list of courses, update the studentList in the corresponding course and return true. Note that a Student can register to a maximum of 6 courses. removeCourse: this method takes as input a course. If the course is not in the list, it returns false. Else, it removes it from the list, updates studentList in the corresponding course and returns true. printSchedule: returns a String with the names of the courses. A Course has a name and a studentList. The class should have a constructor that takes as input the name, a setter and getter for name. The class should have the following methods: AddStudent, printStudents. studentList: use the generic class ArrayList<E> as the type of this attribute AddStudent takes an input a Student If the student is in the list it returns false. Else, it adds the student to the list update the list of courses in this Student and returns true. Note that a course can have a maximum of 30 Students. RemoveStudent: takes as input a Student. If the student is not in the list, it returns false. Else, it removes that student from the list of Students, updates the list of courses for that student, and returns true. printStudents: returns a String which First prints the number of students registered in this course and then prints the name of the Students. • Use appropriate visibility modifiers for attributes and methods Avoid using loops and benefit from the methods provided by the class ArrayList when this is possible • A problem often can be solved in many different ways. Don't hesitate to explore your own solution as long as you match the requirements. Design a test class, where you create 5 five students and three courses. Register each student to two courses. Finally print the Schedule for each Student, and the Students for each course. Questions: 1. Draw the UML diagram. (15 points) 2- Implement the code using netbeans. (75 points) 3. What are the advantages of using the class ArrayList as the type of course List and studentList compared to using arrays ? explain using an example from your code. (5 points) 4. What is generic instantiation ? explain using an example from your code (5 pts) P.S. submit a word document with your answers for Q1, 3, 4 and a netbeans file for Q2.

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Answer 1

Answer #1

Question 1 : (UML diagram)

- 0 X StarUML (UNREGISTERED) File Edit Format Model Tools View Window Debug Help Working Diagrams Model Explorer Q. Main - Mo

In the UML diagram, we will not show the extra generic class ArrayList and the class which contains main(). ArrayList class is already predefined in java but for a clearer understanding, i have written it alongwith the code.

Question 2 :

CODE (with screen shot) :

import java.util.*;
//Generic class for ArrayList
class ArrayList<E> {
List<E> arr;
public ArrayList() {
arr=new java.util.ArrayList<>();
}
public void add(E e) {
arr.add(e);
}
public void remove(E e) {
arr.remove(e);
}
public int size() {
return arr.size();
}
public boolean contains(E e) {
return arr.contains(e);
}

public E get(int i) {
return arr.get(i);
}
}
class Student {
private String name;
private int age;
private String id;
private ArrayList<Course> courseList;
//Generic type ArrayList is used
//Constructor
public Student(String name, int age, String id) {
this.name = name;
this.age = age;
this.id = id;
courseList=new ArrayList<>(); //Instantiate the list
}
//setter and getter methods for each private variable
public void setName(String name) {
this.name = name;
}

public String getName() {
return name;
}

public void setAge(int age) {
this.age = age;
}

public int getAge() {
return age;
}

public void setId(String id) {
this.id = id;
}

public String getId() {
return id;
}
public boolean addCourse(Course course) { //method to add a course to student's course list
if(courseList.contains(course) || courseList.size()==6) {
return false; //Do not add the course if courseList already has the course or it has max 6 courses
} //Otherwise do the following
courseList.add(course); //add course in the courseList
course.addStudent(this); //Also update the studentList for this particular course
return true;
}
public boolean removeCourse(Course course) { //method to remove the course a course from the student course list
if(!courseList.contains(course)) {
return false;
}
courseList.remove(course);
course.removeStudent(this);
return true;
}
public String printSchedule() { //Printing the courses and student informations
String s="";
for(int i=0;i<courseList.size();i++) {
s=s+", "+courseList.get(i).getName();
}
return "\nName : "+name+"\nAge : "+age+"\nID : "+id+"\nCourses : ["+s.substring(1)+" ]";
}
}
class Course {
private String name;
private ArrayList<Student> studentList;
//Constructor for course class which takes as input the name
public Course(String name) {
this.name = name;
studentList = new ArrayList<>();
}
//setter and getter method for the name of course
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
//Adding student to the course
boolean addStudent(Student student) {
if(studentList.contains(student) || studentList.size()==30) {
return false;
}
studentList.add(student);
student.addCourse(this);
return true;
}
//Removing student from the course
boolean removeStudent(Student student) {
if(!studentList.contains(student)) {
return false;
}
studentList.remove(student);
student.removeCourse(this);
return true;
}
//Prints the student list of each course
String printStudents() {
String s="";
for(int i=0;i<studentList.size();i++) {
s=s+", "+studentList.get(i).getName();
}
return "\nNumber of Students attending "+name+" : "+studentList.size()+"\nNames ["+s.substring(1)+" ]";
}
}
class TestStudent { //Tester class as mentioned in the question
public static void main(String[] args) {
Student s1=new Student("John Marcus",24,"S101");
Student s2=new Student("Alina Gilbert",20,"S102");
Student s3=new Student("Henry Roberts",25,"S103");
Student s4=new Student("Jacob Meyer",22,"S104");
Student s5=new Student("Jeremy Dulcet",23,"S105");
Course c1=new Course("Artificial Intelligence");
Course c2=new Course("Image Processing");
Course c3=new Course("Core Java");
s1.addCourse(c1);
s1.addCourse(c2);
s2.addCourse(c3);
s2.addCourse(c2);
s3.addCourse(c3);
s3.addCourse(c3); //Adding c3 to s3 twice, so this will return false because c3 has already been added to student s3
s3.addCourse(c1);
s4.addCourse(c2);
s4.addCourse(c3);
s5.addCourse(c1);
s5.addCourse(c2);
System.out.println(s1.printSchedule());
System.out.println(s2.printSchedule());
System.out.println(s3.printSchedule());
System.out.println(s4.printSchedule());
System.out.println(s5.printSchedule());
System.out.println(c1.printStudents());
System.out.println(c2.printStudents());
System.out.println(c3.printStudents());
}

}

_ JavaApplication 1 - NetBeans IDE 8.2 RC File Edit View Navigate Source Refactor Run Debug Profile Team Tools Window Help <d

_ 0 X JavaApplication1 - NetBeans IDE 8.2 RC File Edit View Navigate Source Refactor Run Debug Profile Team Tools Window Help

_ 0 X JavaApplication 1 - NetBeans IDE 8.2 RC File Edit View Navigate Source Refactor Run Debug Profile Team Tools Window Hel

OUTPUT :

_ JavaApplication 1 - NetBeans IDE 8.2 RC File Edit View Navigate Source Refactor Run Debug Profile Team Tools Window Help <d

Question 3 :

The ArrayList generic type is better than arrays because it saves us a lot of trouble to find out any value or information. It is easier to add and remove any object or value from the arrayList without having to iterate everytime to that index location :

Example consider the code :

boolean addStudent(Student student) {
if(studentList.contains(student) || studentList.size()==30) {
return false;
}
studentList.add(student);
student.addCourse(this);
return true;
}
//Removing student from the course
boolean removeStudent(Student student) {
if(!studentList.contains(student)) {
return false;
}
studentList.remove(student);
student.removeCourse(this);
return true;
}

In this code, we can add and remove data from 'studentList' with just one line of code without any iterations or worrying about its size.

Had it been an array the a for loop would have to be run from 0 upto the last index where value is stored and then it would have been possible to add the object.

Hence we would need to maintain another variable which is size of array, which is not needed in the arrayList.

Also when removing from an array, each time the size of array would have to be reduced. But becuase we are using arrayList, so these mechanisms are automatically done and we need not worry about it.

Question 4 :

Generic instantiation is to decide the type of the class at runtime. It can be any kind of Object but we do not know about it before hand.

Generics helps us in code reusability

For example :

class Stack<E> {

}

This is a generic class of stack. Now we can use this class to create a stack of integers, string values or any other object values and define them at runtime as per convenience inside the main method. This is the advantage of using generics.

Instantiation would be like :

Stack<String> s = new Stack<>();

Example from the code :

class Student {
private String name;
private int age;
private String id;
private ArrayList<Course> courseList;
//Generic type ArrayList is used
//Constructor
public Student(String name, int age, String id) {
this.name = name;
this.age = age;
this.id = id;
courseList=new ArrayList<>(); //Instantiate the list
}

Just look at the consturctor of Student class. we have initialized the ArrayList has type Course which is another class.

This ArrayList is a generic type class itself which can be of any type. In Student class it is of Course type and in Course class it is of Student type.

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