Question

\((\text {Rectangle Class})\) Create a class Rectangle with attributes length and width, each of which defaults to \(1 .\) Provide methods that calculate the rectangle's perimeter and area. It has set and get methods for both length and width. The set methods should verify that Tength and width are each floating- point numbers larger than 0.0 and less than \(20.0 .\) Write a program to test class Rectangle.

Short answer

Class Rectangle is defined with set and get methods for length and width ensuring values are between 0.0 and 20.0. It also includes methods to calculate perimeter and area. The program tests the class by creating an instance and using these methods.

Step-by-step solution

Define the Rectangle Class

Begin by defining the Rectangle class with the attributes 'length' and 'width'. Initialize these attributes in the constructor (__init__ method), setting them to default values of 1 if no arguments are provided. Ensure both are floating-point numbers.

Create Setter Methods

Define setter methods for length and width ('set_length' and 'set_width'). Inside these methods, check that the provided values are floating-point numbers between 0.0 and 20.0 before assigning them to the attributes. If the values are not in this range or not floating-point numbers, raise a ValueError.

Create Getter Methods

Define getter methods for length and width ('get_length' and 'get_width') that simply return the current values of the attributes.

Implement the Perimeter Calculation Method

Create a method 'calculate_perimeter' that computes the perimeter of the rectangle by using the formula: Perimeter = 2 * (length + width).

Implement the Area Calculation Method

Create a method 'calculate_area' that computes the area of the rectangle using the formula: Area = length * width.

Write a Test Program

Write a test program to instantiate a Rectangle object and demonstrate the setting and getting of length and width, as well as the calculations of perimeter and area.

Key concepts

Java programming

Java programming is a computer language used to develop software for multiple platforms. At its core, Java is an object-oriented language, which means that programmers organize code into objects that have attributes and behaviors.

When dealing with a concept like a Rectangle class in Java, the first step is to define the class structure, which acts as a blueprint for creating objects. An essential part of writing a Java program that creates and manipulates rectangles would involve defining the properties such as the length and width of the rectangle, which are treated as attributes of the object. Moreover, Java allows the use of constructors, special methods called when an object is instantiated, to provide default values or initialize the object's state. In our example, the Rectangle's length and width would default to 1.0 if not otherwise specified during object creation.

Encapsulation is also a significant aspect of Java programming, which means restricting direct access to some of an object's components. This is achieved using setter ('set') and getter ('get') methods to control the values of length and width to ensure they remain within the defined constraints (>0 and <20 in this case). Proper error handling through exceptions, like raising a 'ValueError', is crucial to ensure the program behaves correctly when unexpected values are provided.

Object-oriented programming

Object-oriented programming (OOP) is a programming paradigm based on the concept of 'objects', which can contain data, in the form of fields (often known as attributes or properties), and code, in the form of procedures (often known as methods). A key feature of OOP is the ability to create classes, which are blueprints for objects.

In the context of our Rectangle exercise in Java, OOP principles guide the structuring of the program. The Rectangle itself is an object with fields (length and width) and methods to manipulate these fields (set_length, set_width, get_length, get_width). OOP isn't just about representing entities as objects but also involves the principles of encapsulation, inheritance, and polymorphism.

Encapsulation allows us to keep the fields within our Rectangle class private, which is why we use setter and getter methods to interact with these fields. This protects the integrity of our data by ensuring that length and width can only be set to values that meet specific criteria. If this concept is harnessed correctly, it makes our code more flexible and maintainable, one of the significant advantages of OOP.

Class methods and attributes

In object-oriented programming, methods and attributes are two of the primary components of a class. Attributes are the variables that hold data pertaining to the objects, and methods are the functions that define the behavior of the objects.

For instance, in the Rectangle class, the attributes are 'length' and 'width'. These attributes store the numerical values that represent the dimensions of a rectangle. Methods perform operations on these attributes, like 'set_length' and 'set_width', which enforce rules for acceptable values. Other methods like 'calculate_perimeter' and 'calculate_area' define specific computations using the attributes.

It's worth noting that class attributes and methods should be as descriptive and specific as possible to ensure clarity in code. For example, rather than having a method named 'set', naming it 'set_width' makes it explicit that the method is for setting the width attribute of the Rectangle. This distinction helps to avoid confusion and provides a clear understanding of what each part of the code is intended to do, making it easier to read, debug, and maintain.