UML Design lecture recording on 24 February 2025 at 12.18.55 PM

Introduction to Software Design and Class Implementation

• The discussion revolves around designing a class for a Rectangle and a Bank Account in software engineering.

  • Importance of understanding the requirements before starting to write code.

  • Emphasis on creating a UML (Unified Modeling Language) design to visualize class structures.

Step 1: Read the Requirements

• Begin by reading the question or problem requirement.

• Identify key components that need to be implemented:

  • Instance variables (such as dimensions for the Rectangle class).

  • Determine the class structure.

Step 2: UML Design

• Create a UML diagram to represent the structure of the class visually.

  • UML helps in visualizing the attributes (instance variables) and methods (functions) of the class.

  • Use UML representations to document class relationships if applicable.

Step 3: Writing the Constructor

• The constructor is typically defined after establishing the UML design.

  • A constructor initializes instance variables of the class.

  • For example, the Rectangle class constructor may initialize width and height.

Step 4: Example - Designing a Bank Account Class

• Consider the design for a bank account management system.

  • Key interactions include deposits and withdrawals affecting the balance.

Key Design Elements for Bank Account Class

• Class Name: BankAccount

• Instance Variables:

  • username: Represents the account holder's name.

  • balance: Represents the current balance in the account (of type double).

Operations to Implement

• Deposit: Increase the balance when a user deposits money.

• Withdraw: Decrease the balance when a user withdraws money, ensuring there are sufficient funds.

  • If the balance is zero, withdrawals are prohibited.

Step 5: Implementing Class Methods

• Define methods essential to the Bank Account class:

  • Getters:

    • getHolder(): Returns the name of the account holder (String).

    • getBalance(): Returns the current balance (double).

  • Setters:

    • setHolder(String name): Allows updating the account holder's name.

  • Deposit Method:

    • Implement logic to add funds to the balance.

  • Withdraw Method:

    • Implement logic to deduct funds from the balance while checking balance constraints.

Example Code Structure (Pseudocode)

class BankAccount {
    private String username;
    private double balance;

    // Constructor to initialize BankAccount object
    public BankAccount(String username, double balance) {
        this.username = username;
        this.balance = balance;
    }

    // Getters
    public String getHolder() {
        return username;
    }

    public double getBalance() {
        return balance;
    }

    // Setters
    public void setHolder(String name) {
        this.username = name;
    }

    // Methods for deposit and withdrawal
    public void deposit(double amount) {
        this.balance += amount;
    }

    public void withdraw(double amount) {
        if (amount <= balance) {
            this.balance -= amount;
        } else {
            // Handle insufficient balance
        }
    }
}

Conclusion

• The design process is critical in software engineering.

  • Consider all required functionalities and their interactions before coding.

  • Achieve clear structures through UML and methodical coding practices for effective results in programming.

UML Design for BankAccount Class

Class: BankAccount

• Attributes:

  • username: String

  • balance: double

• Methods:

  • BankAccount(String username, double balance)

  • getHolder(): String

  • getBalance(): double

  • setHolder(String name): void

  • deposit(double amount): void

  • withdraw(double amount): void