Java Exercises On Classes And Objects
Gwenda Arguin
Object-oriented programming: Object-oriented programming (OOP) is a programming paradigm based onthe concept of "objects", which can contain data and code. The data is in the form of fields(often known as attributes or properties), and the code is in the form of procedures (often known as methods).
A Java class file is a file (with the .class filename extension) containing Java bytecode thatcan be executed on the Java Virtual Machine (JVM). A Java class file is usually produced by aJava compiler from Java programming language source files (.java files) containing Java classes(alternatively, other JVM languages can also be used to create class files).
If a source file has more than one class, each class is compiled into a separate class file.
1. Write a Java program to create a class called "Person" with a name and age attribute. Create two instances of the "Person" class, set their attributes using the constructor, and print their name and age.
2. Write a Java program to create a class called "Dog" with a name and breed attribute. Create two instances of the "Dog" class, set their attributes using the constructor and modify the attributes using the setter methods and print the updated values.
7. Write a Java program to create a class called "Bank" with a collection of accounts and methods to add and remove accounts, and to deposit and withdraw money. Also define a class called "Account" to maintain account details of a particular customer.
14. Write a Java program to create a class called "School" with attributes for students, teachers, and classes, and methods to add and remove students and teachers, and to create classes.
18. Write a Java program to create a class called "Restaurant" with attributes for menu items, prices, and ratings, and methods to add and remove items, and to calculate average rating.
20. Write a Java program to create a class called "BankAccount" with attributes for account number, account holder's name, and balance. Include methods for depositing and withdrawing money, as well as checking the balance. Create a subclass called "SavingsAccount" that adds an interest rate attribute and a method to apply interest.
21. Write a Java program to create a class called "Vehicle" with attributes for make, model, and year. Create subclasses "Car" and "Truck" that add specific attributes like trunk size for cars and payload capacity for trucks. Implement a method to display vehicle details in each subclass.
22. Write a Java program to create a class called "Customer" with attributes for name, email, and purchase history. Implement methods to add purchases to the history and calculate total expenditure. Create a subclass "LoyalCustomer" that adds a discount rate attribute and a method to apply the discount.
23. Write a Java program to create a class called "Course" with attributes for course name, instructor, and credits. Create a subclass "OnlineCourse" that adds attributes for platform and duration. Implement methods to display course details and check if the course is eligible for a certificate based on duration.
24. Write a Java program to create a class called "ElectronicsProduct" with attributes for product ID, name, and price. Implement methods to apply a discount and calculate the final price. Create a subclass " WashingMachine" that adds a warranty period attribute and a method to extend the warranty.
25. Write a Java program to create a class called "Building" with attributes for address, number of floors, and total area. Create subclasses "ResidentialBuilding" and "CommercialBuilding" that add specific attributes like number of apartments for residential and office space for commercial buildings. Implement a method to calculate the total rent for each subclass.
26. Write a Java program to create a class called "Event" with attributes for event name, date, and location. Create subclasses "Seminar" and "MusicalPerformance" that add specific attributes like number of speakers for seminars and performer list for concerts. Implement methods to display event details and check for conflicts in the event schedule.
27. Write a Java program to create a class called "CustomerOrder" with attributes for order ID, customer, and order date. Create a subclass "OnlineOrder" that adds attributes for delivery address and tracking number. Implement methods to calculate delivery time based on the address and update the tracking status.
28. Write a Java program to create a class called "Reservation" with attributes for reservation ID, customer name, and date. Create subclasses "ResortReservation" and "RailwayReservation" that add specific attributes like room number for hotels and seat number for flights. Implement methods to check reservation status and modify reservation details.
29. Write a Java program to create a class called "Pet" with attributes for name, species, and age. Create subclasses "Dog" and "Bird" that add specific attributes like favorite toy for dogs and wing span for birds. Implement methods to display pet details and calculate the pet's age in human years.
30. Write a Java program to create a class called "GymMembership" with attributes for member name, membership type, and duration. Create a subclass "PremiumMembership" that adds attributes for personal trainer availability and spa access. Implement methods to calculate membership fees and check for special offers based on membership type.
With the knowledge you now have of the basics of the Java programming language, you can learn to write your own classes. In this lesson, you will find information about defining your own classes, including declaring member variables, methods, and constructors.
This lesson also covers nesting classes within other classes, and enumerations ClassesThis section shows you the anatomy of a class, and howto declare fields, methods, and constructors.ObjectsThis section covers creating and using objects. You will learn how to instantiate an object, and, once instantiated, how to use the dot operator to access the object's instance variables and methods.More on ClassesThis section covers more aspects of classes that depend on using object references and the dot operator that you learned about in the preceding section: returning values from methods, the this keyword, class vs. instance members, and access control.Nested ClassesStatic nested classes, inner classes, anonymous innerclasses, local classes, and lambda expressions are covered.There is also a discussion on when to use which approach.Enum TypesThis section covers enumerations, specialized classes that allow you to define and use sets of constants.
Everything in Java is associated with classes and objects, along with its attributes and methods. For example: in real life, a car is an object. The car has attributes, such as weight and color, and methods, such as drive and brake.
You can also create an object of a class and access it in another class. This is often used for better organization of classes (one class has all the attributes and methods, while the other class holds the main() method (code to be executed)).
A class called Employee, which models an employee with an ID, name and salary, is designed as shown in the following class diagram. The method raiseSalary(percent) increases the salary by the given percentage. Write the Employee class.
A class called Account, which models a bank account of a customer, is designed as shown in the following class diagram. The methods credit(amount) and debit(amount) add or subtract the given amount to the balance. The method transferTo(anotherAccount, amount) transfers the given amount from this Account to the given anotherAccount. Write the Account class.
A class called Time, which models a time instance, is designed as shown in the following class diagram. The methods nextSecond() and previousSecond() shall advance or rewind this instance by one second, and return this instance, so as to support chaining operation such as t1.nextSecond().nextSecond(). Write the Time class.
A class called Ball, which models a bouncing ball, is designed as shown in the following class diagram. It contains its radius, x and y position. Each move-step advances the x and y by delta-x and delta-y, respectively. delta-x and delta-y could be positive or negative. The reflectHorizontal() and reflectVertical() methods could be used to bounce the ball off the walls. Write the Ball class. Study the test driver on how the ball bounces.
Write the Book class (which uses the Author class written earlier). Also write a test driver called TestBook to test all the public methods in the class Book. Take Note that you have to construct an instance of Author before you can construct an instance of Book. E.g.,
Take note that both Book and Author classes have a variable called name. However, it can be differentiated via the referencing instance. For a Book instance says aBook, aBook.name refers to the name of the book; whereas for an Author's instance say auAuthor, anAuthor.name refers to the name of the author. There is no need (and not recommended) to call the variables bookName and authorName.
In the earlier exercise, a book is written by one and only one author. In reality, a book can be written by one or more author. Modify the Book class to support one or more authors by changing the instance variable authors to an Author array.
A class called Author, which models an author of a book, is designed as shown in the class diagram. A class called Book, which models a book written by ONE author and composes an instance of Author as its instance variable, is also shown. Write the Author and Book classes.
A class called Customer, which models a customer in a transaction, is designed as shown in the class diagram. A class called Invoice, which models an invoice for a particular customer and composes an instance of Customer as its instance variable, is also shown. Write the Customer and Invoice classes.
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