Expt 1 - Part 1, Part 2 & Part 3

Explanation

This Java code simulates a simple banking system. It allows a user to create a bank account with an account number, holder's name, and an initial balance. Once the account is created, the user can perform several operations: deposit money, withdraw money, and check the current balance. The program uses a menu-driven approach, meaning the user is presented with a list of options and chooses one by entering a number.

Here's a step-by-step breakdown of the logic:

1. BankAccount Class:

   • This class acts as a blueprint for creating bank account objects.
   • Attributes (Instance Variables): It has three private attributes: accNo (account number, an integer), name (account holder's name, a String), and balance (the current amount in the account, a double). The private keyword means these attributes can only be accessed and modified from within the BankAccount class itself, promoting data encapsulation.
   • Constructor: The BankAccount(int accNo, String name, double balance) is a special method called when a new BankAccount object is created. It takes the initial account number, name, and balance as arguments and assigns them to the corresponding attributes of the object being created. The this keyword is used to distinguish between the class's attributes and the constructor's parameters.
   • deposit(double amount) Method: This method takes a double value representing the amount to deposit. It checks if the amount is positive. If it is, the amount is added to the balance, and a confirmation message is printed. If the amount is not positive, an error message is displayed.
   • withdraw(double amount) Method: This method takes a double value for the withdrawal amount. It first checks if the amount is positive and if there are sufficient funds (amount <= balance). If both conditions are met, the amount is subtracted from the balance, and a confirmation message is printed. Otherwise, an "Insufficient balance or invalid amount!" message is shown.
   • showBalance() Method: This method simply prints the current value of the balance attribute to the console.

2. progx2 Class (Main Program):

   • This is the main class that contains the main method, the entry point of the program.
   • Input Handling: It uses a Scanner object to read input from the user via the console.
   • Account Creation:
     • It prompts the user to enter the account number, name, and initial balance.
     • input.nextLine(); // consume newline is a crucial line. After reading an integer (accNo) with nextInt(), the newline character entered by the user remains in the input buffer. If this line is omitted, the subsequent input.nextLine() for reading the name would incorrectly read this leftover newline instead of waiting for the user's name input.
     • It then creates a BankAccount object named account using the new keyword and the BankAccount constructor, passing the user-provided details.
   • Menu and Operations:
     • A do-while loop is used to repeatedly display a menu of options (Deposit, Withdraw, Show Balance, Exit) and process the user's choice until the user chooses to exit (option 4).
     • A switch statement handles the user's choice:
       • Case 1 (Deposit): Prompts for the deposit amount, calls the account.deposit() method, and then calls account.showBalance() to display the updated balance.
       • Case 2 (Withdraw): Prompts for the withdrawal amount, calls the account.withdraw() method, and then calls account.showBalance() to display the updated balance.
       • Case 3 (Show Balance): Directly calls account.showBalance().
       • Case 4 (Exit): Prints an "Exiting Program" message, which terminates the do-while loop.
       • Default: Handles any invalid menu choices.
   • Resource Cleanup: input.close() is called at the end to release the system resources used by the Scanner.

Algorithm

1. Define a BankAccount class with private attributes for account number, name, and balance.
2. Implement a constructor for BankAccount to initialize these attributes.
3. Implement a deposit method that:
   • Accepts a deposit amount.
   • Validates if the amount is positive.
   • Updates the balance if valid.
   • Prints a confirmation or error message.
4. Implement a withdraw method that:
   • Accepts a withdrawal amount.
   • Validates if the amount is positive and if sufficient balance exists.
   • Updates the balance if valid.
   • Prints a confirmation or error message.
5. Implement a showBalance method to display the current balance.
6. In the main method of progx2 class:
   • Create a Scanner object for user input.
   • Prompt the user for account number, name, and initial balance.
   • Create an instance of the BankAccount class using the provided details.
   • Start a do-while loop for the menu.
   • Inside the loop:
     • Display the menu options (Deposit, Withdraw, Show Balance, Exit).
     • Read the user's choice.
     • Use a switch statement to handle the choice:
       • If Deposit: Prompt for amount, call deposit(), call showBalance().
       • If Withdraw: Prompt for amount, call withdraw(), call showBalance().
       • If Show Balance: Call showBalance().
       • If Exit: Print exit message and set loop condition to terminate.
       • If invalid choice: Print an error message.
   • Close the Scanner object.