Java Example 1

import java.util.ArrayList;
import java.util.Scanner;

// Kaizer here. I created a banking system, which allows you to create your own account, withdraw money, input account numbers, initial balance, and so on and so forth.

// class to represent a bank account
class Account {
    private String accountNumber;
    private String accountHolder;
    private double balance;

    // constructor for initializing account details
    public Account(String accNumber, String accHolder, double initialBalance) {
        this.accountNumber = accNumber;
        this.accountHolder = accHolder;
        this.balance = initialBalance;
    }

    // function to find an already existing account number
    public String getAccountNumber() {
        return accountNumber;
    }

    // function to deposit money into the account
    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
            System.out.println("Deposited: " + amount);
        } else {
            System.out.println("Invalid deposit amount.");
        }
    }

    // function to withdraw money from the account
    public void withdraw(double amount) {
        if (amount > 0 && amount <= balance) {
            balance -= amount;
            System.out.println("Withdrew: " + amount);
        } else {
            System.out.println("Invalid withdrawal amount or insufficient funds.");
        }
    }

    // function to check the account balance
    public double getBalance() {
        return balance;
    }

    // function to display account details
    public void display() {
        System.out.println("Account Number: " + accountNumber);
        System.out.println("Account Holder: " + accountHolder);
        System.out.println("Balance: " + balance);
    }
}

// public Class to manage multiple accounts
class Bank {
    private ArrayList<Account> accounts;

    public Bank() {
        accounts = new ArrayList<>();
    }

    // function to create a new account
    public void createAccount(String accNumber, String accHolder, double initialBalance) {
        accounts.add(new Account(accNumber, accHolder, initialBalance));
        System.out.println("Account created successfully.");
    }

    // function to find an account by account number
    public Account findAccount(String accNumber) {
        for (Account account : accounts) {
            if (account.getAccountNumber().equals(accNumber)) {
                return account;
            }
        }
        return null;
    }

    // function to display all accounts
    public void displayAllAccounts() {
        for (Account account : accounts) {
            account.display();
            System.out.println("-------------------");
        }
    }
}

public class BankingSystem {
    public static void main(String[] args) {
        Bank bank = new Bank();
        Scanner scanner = new Scanner(System.in);
        int choice;
        String accNumber, accHolder;
        double amount;

        do {
            System.out.println("1. Create Account");
            System.out.println("2. Deposit");
            System.out.println("3. Withdraw");
            System.out.println("4. Check Balance");
            System.out.println("5. Display All Accounts");
            System.out.println("6. Exit");
            System.out.print("Enter your choice: ");
            choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    System.out.print("Enter account number: ");
                    accNumber = scanner.next();
                    System.out.print("Enter account holder name: ");
                    accHolder = scanner.next();
                    System.out.print("Enter initial balance: ");
                    amount = scanner.nextDouble();
                    bank.createAccount(accNumber, accHolder, amount);
                    break;
                case 2:
                    System.out.print("Enter account number: ");
                    accNumber = scanner.next();
                    Account account = bank.findAccount(accNumber);
                    if (account != null) {
                        System.out.print("Enter amount to deposit: ");
                        amount = scanner.nextDouble();
                        account.deposit(amount);
                    } else {
                        System.out.println("Account not found.");
                    }
                    break;
                case 3:
                    System.out.print("Enter account number: ");
                    accNumber = scanner.next();
                    account = bank.findAccount(accNumber);
                    if (account != null) {
                        System.out.print("Enter amount to withdraw: ");
                        amount = scanner.nextDouble();
                        account.withdraw(amount);
                    } else {
                        System.out.println("Account not found.");
                    }
                    break;
                case 4:
                    System.out.print("Enter account number: ");
                    accNumber = scanner.next();
                    account = bank.findAccount(accNumber);
                    if (account != null) {
                        System.out.println("Balance: " + account.getBalance());
                    } else {
                        System.out.println("Account not found.");
                    }
                    break;
                case 5:
                    bank.displayAllAccounts();
                    break;
                case 6:
                    System.out.println("Exiting...");
                    break;
                default:
                    System.out.println("Invalid choice. Please try again.");
            }
        } while (choice != 6);

        scanner.close();
    }
}