CR-MacroLabs-OOP-InstructorStudentClassroom

Leon's Lengthy Learner Lab

• Purpose - to demonstrate the use of Java interfaces
• Objective - to implement a ZipCodeWilmington class which mediates a composite Students and Instructors singleton reference.

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Part 1.0 - Test Person

• Create a PersonTest class.
  • Create a testConstructor method which ensures that a Person object's id field is being set upon construction. To check if the id has been set, call the getId() method of the person class which will return a long
    • Create a Person class.
    • In the Person class, declare a final field named id of type long.
    • Create a getter for the id field
  • Create a testSetAndGetName method which ensures that a Person object's name variable is being set by invoking the .setName method and when you call getName() it will return the name you set
    • In the Person class, declare a field named name of type String.
    • The Person class should define a getName() method which returns the Person object's name field.
    • The Person class should define a setName() method which sets the Person object's name field.

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Part 2.0 - Create Learner Interface

• Create a Learner interface.
  • Learner should declare one method signature:
    • Method name: learn
    • Method parameters: double numberOfHours
    • Method return-type: void

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Part 3.0 - Test Student

• Create a StudentTest class.
  • Create a testImplementation method that asserts that a Student is an instanceof a Learner.
    • Create a Student class
    • Student implements the Learner interface
    • Add a dummy implementation for the learn method
  • Create a testInheritance method that asserts that a Student is an instanceof a Person.
    • Make the Student class inherit from Person
  • Create a testLearn method that ensures a Student's totalStudyTime instance variable is incremented by the specified numberOfHours by invoking the .learn method.
    • In the Student class, add a field called totalStudyTime of type double
    • In the Student class, implementate the learn method which increments the totalStudyTime variable by the specified numberOfHours argument.`
    • In the Student class, add a getTotalStudyTime() method which returns the totalStudyTime instance variable.

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Part 4.0 - Create Teacher Interface

• Create a Teacher interface.

  • Teacher should declare a teach method signature:

    • Method name: teach
    • Method parameters:
      • Learner learner
      • double numberOfHours
    • Method return-type: void

  • Teacher should declare a lecture method signature:

    • Method name: lecture
    • Method parameters:
      • Learner[] learners
      • double numberOfHours
    • Method return-type: void

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Part 5.0 - Test Instructor

• Create a InstructorTest class.

  • Create a testImplementation method that asserts that an Instructor is an instanceof a Teacher.

    • Create an Instructor class such that:
      • Instructor implements the Teacher interface
        

  • Create a testInheritance method that asserts that a Instructor is an instanceof a Person.

    • Make the Instructor a subclass of Person

  • Create a testTeach method that ensures when an Instructor invokes the teach method, a respective student's totalStudyTime instance variable is incremented by the specified numberOfHours.

    • In the Instructor class, add a concrete implementation of the teach method which invokes the learn method on the specified Learner object.

  • Create a testLecture method that ensures when an Instructor invokes the lecture method, a respective array of students' totalStudyTime instance variables is incremented by numberOfHours/students.length.

    • Instructor should have a concrete implementation of the lecture method which invokes the learn method on each of the elements in the specified array of Learner objects.
      • numberOfHours should be evenly split amongst the learners.
        • double numberOfHoursPerLearner = numberOfHours / learners.length;

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Part 6.0 - Test People

• Create a PeopleTest class.
• Create a testAdd method which ensures that our personList in our People class populated with respective Person objects following invokation of the add method.
  • Create a People class.
  • The People class should instantiate an ArrayList field of Person objects named personList.
  • The People class should define a method named add which adds a Person to the personList.
  • The People class should define a method named getCount which returns the size of personList.
• Create a testRemoveByPerson method which ensures that the personList in a People object is depopulated with a respective Person object following the invokation of the remove method.
  • The class should define a method named remove which makes use of a Person person parameter to remove a respective Person object.
• Create a testRemoveById method which ensures that the personList in a People object is depopulated with a respective Person object following the invokation of the remove method.
  • The class should define a method named remove which makes use of a long id parameter to remove a Person object with the respective id field.
• Create a testFindById method which ensures that a respective Person object with a respective id field is returned upon invokation of the findById method on a respective People object.
  • The class should define a method named findById which makes use of a long id parameter to return a Person object with the respective id field.
• Create a testGetArray which ensures the array has all the people added
  • In the People class, define a method named getArray which returns an array representation of the personList field.
• Create a testRemoveAll method which ensures you remove all the person added
  • In the People class, define a method named removeAll which clears our personList field.

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Part 7.0 - Test Students singleton

• Note: The creation of the Students will demonstrate an implementation of singleton design pattern.
• Create a StudentsTest class.
• Create a testSingletonInstance method which ensures that calling Students.getInstance() twice will return the same instance. You can check if they are the same instance by calling the Assert.assertSame(instance1, instance2) method.
  • Create a Students class.
  • The class should be an unextendable subclass of the People class.
  • The class should statically instantiate a final field named INSTANCE of type Students.
  • The class should define a private nullary constructor
  • The class should define a getInstance method which returns the INSTANCE field.
• Create a testInitializationSetupStudents method which ensures that each of the students in your current cohort are in your Students singleton when getArray is called.
  • In the constructor of the Students class, add all the students from your class so that calling getArray will return all the students from your cohort
  • Each student should have a relatively unique id field.

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Part 8.0 - Create and Test Instructors singleton

• Use Part 7 as a reference.
• Create a InstructorsTest class.
• Create a Instructors singleton which represents the set of instructors at ZipCodeWilmington.

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Part 9.0 - ZipCodeWilmington

• Create a ZipCodeWilmingtonTest class.
  • Create a testHostLecture method which ensures that each of the Student's totalStudyTime instance variable is incremented by the specified numberOfHours upon invoking the hostLecture method.
  • Create a ZipCodeWilmington singleton.
    • The class should declare a field that references the instance of Students called students.
    • The class should declare a field that references the instance of Instructors called instructors.
    • The class should define a method hostLecture which makes use of a Teacher teacher, double numberOfHours parameter to host a lecture to the composite people field in the students reference.
    • The class should define a method hostLecture which makes use of a long id, double numberOfHours parameter to identify a respective Instructor to host a lecture to the composite people field in the cohort reference.

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Notice the Design Flaw - Odd Casting Issues

• You may have noticed that the findById, and hostLecture methods require an intermediate casting trick.
• To remedy this issue, we can generify the People class.

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Part 10.1 - Modify People class

• Parameterize the People signature to enforce that it is a container for objects of type E such that E is a subclass of Person.
• Modify the class signature to declare this class abstract.
  • An abstract class cannot be instantiated; Its concrete implementation is deferred to its subclass.
• Modify people field to enforce that is a container of objects of type E.
• Modify the add method to ensure that it handles object of type E.
• Modify the findById method to ensure that it returns an object of type E.
• Modify the getArray method signature by declaring it abstract of return type E.
  • An abstract method is a subclass's contractual agreement to the deferment of an implementation of a respective method.
• You may need to create an inner class to test make the People class

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Part 10.2 - Modify People subclasses

• Modify the Students class signature to ensure that it is a subclass of People of parameterized type Student.
• Modify the Instructors class signature to ensure that it is a subclass of People of parameterized type Instructor.
• See if you can modify the getArray method in the People class to return the generic array back. Otherwise, add concrete implementations of the getArray method in each of these classes
  • HINT: To create a new generic array, you can use E[] array = (E[]) Array.newInstance(Student[].class.getComponentType(), list.size());. Note in this code, when I call newInstance, I give the Student[].class. Change it so it can be Student[] or Instructor[] or Person[].

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Part 10.3 - Refactor ZipCodeWilmington class

• Refactor the hostLecture method in the ZipCodeWilmington class by removing any intermediate casting trick(s).

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Part 10.4 - Test refactored classes.

• Ensure that the StudentsTest, InstructorsTest, PeopleTest, ZipCodeWilmingtonTest classes were not affected by the refactor.

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Notice the Design Flaw - Non-Intuitive Orientation

• You may have noticed that findById makes it difficult to intuitively identify which Person object is being returned. To remedy this issue, we can make use of an enum which manipulates a composite instructor object.

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Part 11.1 - Create Educator enum

• Create an enum named Educator.
  • The enum should implement Teacher.
  • The enum should have an enumeration for each of the instructors represented in the Instructors class.
  • Calls to the teach and lecture method should be differed to the composite instructor reference.
  • The enum should have a double timeWorked field which keeps track of the hours that the Educator has taught.
• In the constuctor of the Instructors class, get all the Educator by calling Educator.values(), add all the instructor to Upon construction each enumeration of the enum should instantiate a respective Instructor and assign it to a final instructor field upon construction. The instructor should be added to the Instructors singleton.

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Part 11.0 - Test Educator

• Use Part 5 as a reference.

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Part 12.0 - Test ZipCodeWilmington

• Ensure the hostLecture method can handle objects of type Educator.