An introduction to using classes and constructors in the Java programming language.

This is a lab used in Computer Science II (CSCE 156) for Fall 2023 in the School of Computing at the University of Nebraska-Lincoln.

• Java constructor tutorial:
  https://docs.oracle.com/javase/tutorial/java/javaOO/constructors.html

• Object Creation tutorial:
  http://download.oracle.com/javase/tutorial/java/javaOO/objectcreation.html

Following the lab, you should be able to:

• Use Classes and objects to write Java programs

• Understand and use constructors

• Understand the visibility of a class's methods and how to use them

Note that the lab may involve some concepts, classes, or methods not covered (yet) in the class. You should be able to complete the lab without fully understanding them. If you have any questions about them, please feel free to ask our LAs.

At the start of each lab, you may find a team member by yourself or may be randomly paired up with another student by a lab instructor. One of you will be designated the driver and the other the navigator. If you prefer to work on this lab by yourself, that is fine too. Each week you should try to alternate: if you were a driver last week, be a navigator next, etc.

Note that, each student must submit the code to CodePost for grading.

Clone this project code for this lab from GitHub in Eclipse using the URL: https://github.com/lisongxu/CSCE156-Lab-OOP-Basic

Java is a class-based Object Oriented Programming Language meaning that it realizes the concept of objects by allowing you to define classes which have member methods and variables. Instances of classes are created through a constructor, which is a method with the same name as a class and called using the keyword new. This lab will familiarize you with how classes and their constructors are defined and used. In addition, you will be introduced to some ways that Java supports other Object Oriented Principles: Encapsulation and Abstraction.

• Encapsulation is a mechanism by which objects group data and the methods/functions that act on that data.

• Abstraction refers to the means by which an object exposes a public interface to the outside world while hiding the inner workings (the internal representation or the implementation details). Java achieves this by allowing you to define member methods and variables and to specify the visibility of these fields using the keywords private, protected, and public.

• Class Signaling refers to invoking methods on an instance of a class. Java uses the dot (or period) operator to signal a class.

We have provided a Java project that simulates a library collections system. It has several classes already defined to model authors, books, a library (a collection of books) and a text-based interface which allows you to search the collection, add books to the collection, and list the collection.

1. Run the library demo program LibraryDemo.java to familiarize yourself with its functionality. Note that (3) Printing Collection is not fully operational yet.

2. Modify the Book class by implementing the constructor and the getter (accessor) methods as listed below. Practice Tip: always use the this keyword to disambiguate the scope of variables and prevent potential problems when subclassing.

public Book(String title, Author author, String isbn, String publishDate)
public Author getAuthor()
public String getISBN()
public String getTitle()

3. Test whether your methods work by running the library demo program again. (3) Print Collection should work if all your methods work. Also test your Book class using the JUnit test suites provided in BookTests.java.

The Book class is well-designed: it logically groups data and methods together that semantically define what a book is and how you can use it. The Author class however, is not well-designed. Its data members are publicly exposed and it has no methods at all.

1. Redesign the Author class and make its member variables private.

2. Create and use getter methods to make the members accessible to the outside world. Use these methods where appropriate.

public String getFirstName() 
public String getLastName()

3. Create setter methods (also called mutator methods) to enable code outside of the Author class to change the member variables. Add some data validation: for example, do not allow "invalid" values for member variables.

public void setFirstName(String firstName)
public void setLastName(String lastName)

4. Add and make use of an appropriate constructor to this class.

public Author()
public Author(String firstName, String lastName)

5. Test your Author class using the JUnit test suites provided in AuthorTests.java.

• Test your programs locally on your computer using the provided JUnit test suites. Fix any errors and completely debug your programs.
• Submit the following file to CodePost:
  • Author.java
  • Book.java
• Make sure that your programs pass the tests on CodePost. For this lab, as long as your programs pass the tests on Codepost, you will get full points for the lab.