Object Oriented Programming in Java
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Questions and Answers

What is the purpose of using a static method in a class?

  • To communicate with instance fields of the class.
  • To limit method access to only private classes.
  • To allow multiple instances of a class to share the same method.
  • To create utility functions that can be called at the class level. (correct)

    • What will happen if a static method tries to access an instance field?

  • It will work if the instance is passed to the method.
  • It will cause a compile-time error. (correct)
  • It will be treated as a static field.
  • It will return the value of the instance field.

    • In the provided example, what is the role of 'car.count' in the context of static fields?

  • It allows for individual instances of count across different cars.
  • It accesses the static field count directly using the class name. (correct)
  • It initializes a new instance of the car class.
  • It creates a new instance of count.

    • In the definition of the car class, what happens every time a new instance of car is created?

    <p>The static field count is incremented.</p> Signup and view all the answers

    What keyword is used in Java to define a static method?

    <p>static</p> Signup and view all the answers

    Which operation allows for changing a student's academic standing?

    <p>Change Level()</p> Signup and view all the answers

    What data is NOT commonly associated with a student in this context?

    <p>Job Title</p> Signup and view all the answers

    Which of the following options is a method to modify a student's GPA?

    <p>Modify GPA()</p> Signup and view all the answers

    What additional data attribute is present in Student 2 but not in Student 1?

    <p>Email</p> Signup and view all the answers

    Which operation does NOT belong to the Student class?

    <p>Calculate Age()</p> Signup and view all the answers

    Which data element represents a unique identifier for each student?

    <p>University ID</p> Signup and view all the answers

    Which operation is used to change a student's name?

    <p>Set Name()</p> Signup and view all the answers

    What is the purpose of the Print Student Info() operation?

    <p>To display a student's information</p> Signup and view all the answers

    What is the purpose of the 'Modify GPA()' function in the context of the student class?

    <p>To update the GPA of the student.</p> Signup and view all the answers

    Which access modifier is applied to the 'length' and 'width' attributes of the rectangle class?

    <p>Private</p> Signup and view all the answers

    How can the attributes of the 'student' class be accessed outside the class?

    <p>By using public methods.</p> Signup and view all the answers

    Given the student object 'myS', what is the value of 'myS.GPA' after initialization?

    <p>2.5</p> Signup and view all the answers

    What is the output of calling 'Print Student Info()'?

    <p>It displays the student's ID, University_ID, GPA, and Address.</p> Signup and view all the answers

    What does the 'setLength()' method do in the context of the rectangle class?

    <p>It sets a new value for the rectangle's length.</p> Signup and view all the answers

    What is the initial value of 'myS.Address' according to the initialization in the student class?

    <p>Kafr El-Shiekh</p> Signup and view all the answers

    What is the role of the 'getWidth()' method in the rectangle class?

    <p>To retrieve the current width value.</p> Signup and view all the answers

    What is the purpose of data hiding in a class?

    <p>To protect the integrity of an object's internal data.</p> Signup and view all the answers

    Which of the following is a true statement about constructors?

    <p>Constructors are called when an object is created.</p> Signup and view all the answers

    What will happen if a local reference variable is declared but not initialized?

    <p>It will result in a compiler error when accessed.</p> Signup and view all the answers

    In the provided class, what is a consequence of attempting to directly access the private field 'length' from outside the class?

    <p>It will result in a compile-time error.</p> Signup and view all the answers

    What does the getArea() method in the rectangle class return?

    <p>Length multiplied by width.</p> Signup and view all the answers

    What must be true about the 'setLength' method in the rectangle class?

    <p>It accepts a parameter to set the length.</p> Signup and view all the answers

    Which of the following statements about the rectangle class's width field is accurate?

    <p>It can only be modified using setWidth method.</p> Signup and view all the answers

    Why is it essential that a constructor has no return type?

    <p>To distinguish it from ordinary methods.</p> Signup and view all the answers

    What is method overloading?

    <p>Defining multiple methods with the same name but different parameters.</p> Signup and view all the answers

    Which of the following is NOT a reason to use method overloading?

    <p>To restrict access to class functionality.</p> Signup and view all the answers

    What happens when a rectangle is created using the constructor with parameters?

    <p>The width and length are initialized to specific values provided by the user.</p> Signup and view all the answers

    Which of the following constructors can be used to create an Employee object with default settings?

    <p>Employee()</p> Signup and view all the answers

    In the Employee class, which data member is initialized with a specific value in the default constructor?

    <p>Salary</p> Signup and view all the answers

    What does the method getArea() likely do in the rectangle class?

    <p>Returns the area of the rectangle based on its dimensions.</p> Signup and view all the answers

    What is the outcome when the constructor 'Employee(int id, String name)' is called?

    <p>Emp_ID is set and Name is initialized.</p> Signup and view all the answers

    Which of the following statements about static members in a class is true?

    <p>Static members can be accessed without an instance of the class.</p> Signup and view all the answers

    What will happen if two methods in the same class have the same name but the same parameters?

    <p>An error will occur during compilation.</p> Signup and view all the answers

    What is a benefit of constructor overloading?

    <p>It allows different initialization options for objects.</p> Signup and view all the answers

    In the given Employee class, which constructor allows initialization of all attributes?

    <p>Employee(int id, String name, double salary, double bonus)</p> Signup and view all the answers

    What does the presence of multiple overloaded constructors in a class enable?

    <p>Providing different means to create objects using varied parameters.</p> Signup and view all the answers

    When calling a parameterized constructor of the Employee class, which attributes will remain uninitialized if the constructor doesn't set them?

    <p>Some attributes may remain NULL if not explicitly set.</p> Signup and view all the answers

    Study Notes

    Object Oriented Programming

    • In object-oriented programming, data and operations are grouped together to create an object.
    • An object is an instance of a class.
    • A class is a blueprint for creating objects.
    • Student class:
      • Data members (attributes): student name, university ID, birth date, address, GPA, study level, email.
      • Operations (methods): modify GPA, change level, set name, set address, print student info.

    First Class in Java

    • student class:
      • Data members: ID, University_ID, GPA, Address.
      • The class is declared using the public class student keyword.
      • Each data member is declared with a data type (int, double, or String).
      • An object is created using the new keyword.
      • An object is accessed using the dot operator (.).

    Access Modifier

    • Private modifier:
      • Restricts access to class members from outside the class.
    • Public modifier:
      • Allows access to class members from inside or outside the class.

    Data Hiding

    • Encapsulation is the process of hiding data members and operations within a class.
    • This promotes code integrity by restricting direct access to internal data and enforcing access through methods.

    Constructor

    • A constructor is a special method that is called when an object is created.
    • Constructors have the same name as the class.
    • Constructors do not have a return type.
    • Constructors are typically public.

    Overloading Methods and Constructors

    • Method overloading allows for multiple methods with the same name but different parameter lists.
    • Constructor overloading allows for multiple constructors with different parameter lists.

    Example of Class Employee

    • Employee class:
      • Data members: Emp_ID, Name, Depart, Salary, bonus, Resident.
      • Methods:
        • Multiple constructors with different parameters to initialize the object.
        • Set_Salary(), which takes a double value and sets the employee's salary.
        • Set_Depart(), which takes a String value and sets the employee's department.
        • Set_Emp_ID(), which takes an integer value and sets the employee's ID.
        • Print_Emp_Data(), which prints the employee's data.

    Static Class Members

    • Static fields and methods belong to the class, not individual objects.
    • Static fields are accessed using the class name, not object name.
    • Static methods cannot access instance fields, only static ones.
    • They are typically used to create utility classes, like the Math class in Java.

    Uninitialized Local Reference Variables

    • Variables declared in a method can be initialized without assigning a value, making them uninitialized until assigned.
    • Using an uninitialized reference variable leads to a compiler error.

    Rectangle Class

    • rectangle class:
      • Data members: length, width.
      • Methods:
        • Set methods: setLength(), setWidth().
        • Get methods: getLength(), getWidth(), getArea().

    Initializing Value Through Constructors

    • Constructors are called when objects are instantiated, allowing initialization of data members without explicit assignments.

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    Lecture 2 - Object Oriented Programming PDF

    Description

    This quiz covers the fundamentals of Object-Oriented Programming (OOP) in Java, focusing on concepts such as classes, objects, data members, and access modifiers. Explore the definitions and functionalities of a student class, including its attributes and methods.

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