Question

Create a class called Date that includes three pieces of information as instance variables- \(a\) month (type int), a day (type int) and a year (type int). Your class should have a constructor that initializes the three instance variables and assumes that the values provided are correct. Provide a set and a get method for each instance variable. Provide a method displayDate that displays the month, day and year separated by forward slashes ( \(/\) ). Write a test application named DateTest that demonstrates class Date's capabilities.

Short answer

Define a `Date` class, implement constructor, getters, and setters, and test using `DateTest` class with a `displayDate` method.

Step-by-step solution

Define the Date Class

Begin by defining the class `Date`. Include three instance variables: `month`, `day`, and `year`, each of type `int`. These variables will store the date information.

Create the Constructor

Define the constructor for the `Date` class. This constructor should take three parameters corresponding to the month, day, and year. Initialize the instance variables with these parameters. Assume the values provided are valid.

Define Getter Methods

Create getter methods for each of the instance variables. These methods should be named `getMonth()`, `getDay()`, and `getYear()`. They should return the respective instance variable value.

Define Setter Methods

Develop setter methods for each instance variable. The methods should be `setMonth(int month)`, `setDay(int day)`, and `setYear(int year)`. Assign the parameter values to the respective instance variables.

Implement displayDate Method

Implement the `displayDate()` method in the `Date` class. This method should output the date in the format month/day/year using a print statement.

Create DateTest Class

Develop a `DateTest` class to test the `Date` class. In this class, create an instance of `Date` and demonstrate the use of each `get` and `set` methods, as well as the `displayDate` method.

Test the Application

Within the `DateTest` class, use the `set` methods to modify the month, day, and year and then display the date using `displayDate()` to showcase the functionality of the `Date` class.

Key concepts

Object-Oriented Programming

Object-Oriented Programming (OOP) is a programming paradigm centered around objects rather than actions. In OOP, objects are instances of classes, which are templates for creating these objects. Each object can contain data and methods that operate on the data. OOP promotes greater modularity and reusability through encapsulation, inheritance, and polymorphism.

In Java, OOP allows developers to create classes that can define the structure of objects, including their fields (attributes), and behaviors (methods). With OOP, you encapsulate your data and ensure that developers use your software in the intended way, enhancing maintainability and flexibility of code.

Java Classes and Objects

In Java, a class is a blueprint from which individual objects are created. It holds definitions for the properties and behaviors of its objects. For example, the `Date` class is used to create `Date` objects with specific attributes like month, day, and year.

• **Class Syntax:** To define a class, use the keyword `class` followed by the class name.
• **Object Creation:** You create an object using the `new` keyword followed by the class constructor.

A class typically includes fields (variables) to hold the state of the object and methods to define its behavior. With classes, you can instantiate multiple objects, each containing its own data.

Java Methods

Methods in Java define actions or behaviors for classes and objects. Methods are similar to functions and can perform operations, return values, or modify the state of an object.

Java methods consist of a declaration and a body. The declaration includes the method's name, return type, and parameters, while the body contains the statements which execute the method's functionality. Common methods found in classes include `get` methods, which return data, and `set` methods, which allow you to modify data.

• **Get Methods:** Return the current value of an object's attribute.
• **Set Methods:** Allow modification of an attribute's value.

Methods help encapsulate functionality, making it easier to reuse and maintain code.

Java Instance Variables

Instance variables in Java are non-static fields defined in a class. They hold the values that form part of the object's state. For each instance of a class, a separate set of instance variables is created.

In our `Date` class example, `month`, `day`, and `year` are instance variables. Each `Date` object will have its own unique values for these variables. Instance variables are accessible in all methods within the class, allowing them to be used throughout the class to control and store the object's state.

• They are declared within the class but outside any method.
• They are initialized when an object is created, either explicitly or by the constructor.

Instance variables help define the attributes that differentiate each object created from the same class template.