Question

Develop a Java application that determines whether any of several department- store customers has exceeded the credit limit on a charge account. For each customer, the following facts are available: a) account number b) balance at the beginning of the month c) total of all items charged by the customer this month d) total of all credits applied to the customer's account this month e) allowed credit limit.

Short answer

The Java application requires implementing a Customer class to handle customer data, calculating new balances, and checking against credit limits. The main method will loop to input data for each customer and report if their credit limit has been exceeded.

Step-by-step solution

Understand the problem

The task is to create a Java application that will process customer account information and determine if the customer has exceeded their credit limit. To do this, the program will need to take several pieces of information for each customer - the starting balance, total charges, total credits, and credit limit - then perform calculations to determine the new balance and compare it to the allowed credit limit.

Define the Customer class

Define a Customer class with private instance variables to hold the account number, balance at the beginning of the month, total charges, total credits, and credit limit. Include a constructor to initialize these variables and a method to calculate the new balance by adding charges and subtracting credits from the initial balance. Also, include a method 'checkCreditLimit' to determine if the new balance exceeds the credit limit.

Create a method to input customer data

Create a method, possibly named 'inputCustomerData', for collecting the customer's data from the user or an external source. The method should prompt for and receive the account number, balance at the beginning of the month, total charges, total credits, and credit limit.

Implement the credit limit check

In the Customer class, implement a method 'checkCreditLimit' that compares the calculated new balance with the allowed credit limit. If the new balance exceeds the credit limit, the method should print a message indicating the account number and that the credit limit has been exceeded.

Main application loop

Write the 'main' method of your Java application. This method should initiate the input process for each customer, create a new Customer object with the input data, perform the credit limit check, and repeat this process for as many customers as necessary.

Test the Application

After completing the application, run it with various test cases to ensure that it correctly calculates the new balance and accurately determines whether the credit limit has been exceeded for each customer.

Key concepts

Object-Oriented Programming

Object-Oriented Programming (OOP) is a programming paradigm centered on the concept of 'objects', which can contain data in the form of fields, often known as attributes, and code, in the form of procedures, often known as methods. One of the core principles of OOP is encapsulation, which means that the internal representation of an object is hidden from the outside, only allowing access through a public set of functions.

Java, as an object-oriented language, excels in solving problems that have real-world counterparts, like our credit limit checker application exemplifies. In this context, the 'Customer' is conceptualized as an object with properties such as account number and balance. In Java, a 'class' serves as a blueprint for objects, defining what attributes they contain and behaviors they can perform, ensuring that each object created from the class has the necessary structure to represent a customer in our application.

Achieving such a structure not only helps in organizing code better but also provides a smooth pathway for implementing functionality such as inheritance and polymorphism, which are other pillars of OOP. This makes the codebase more flexible and easier to maintain over time.

Class Definition in Java

In Java, a class is defined as a template that describes the behavior and state that objects of its type support. Classes are essential as they help us to encapsulate and structure our code more effectively. For our Credit Limit Checker application, the 'Customer' class is pivotal. It organizes customer data and provides methods that operate on this data.

Key Components of a Class

Within the Customer class, there are several key components:

• Attributes: These are the variables that hold data, such as account number and credit limit.
• Constructor: A special method used to initialize new objects. It sets up the initial state.
• Methods: They define behaviors - such as calculating a new balance or checking the credit limit.

Each of these components plays a role in ensuring that when a Customer object is instantiated, it can perform necessary operations – like checking if the credit limit has been exceeded. Careful definition of a class in Java can greatly simplify complex problems by breaking them down into manageable chunks.

Conditional Statements in Java

Conditional statements are fundamental to programming in Java. They allow the application to make decisions and execute code based on certain conditions. In our Credit Limit Checker application, the conditional statement comes into play in the 'checkCreditLimit' method.

Here's a simplified look at how this works:

• The program calculates the new balance for a customer.
• It then checks if the new balance is greater than the allowed credit limit using an 'if' statement.
• If the condition evaluates to true, the program executes the code block that prints out the message indicating the credit limit is exceeded.

Without conditional statements, it would be impossible to handle logic that requires branching, which is central to most applications. By employing conditional logic, Java applications like our Credit Limit Checker become dynamic and responsive to different data inputs, allowing for complex decision-making based on customer data.