main.dart

import 'dart:math';

void main() {
  // user1
  final user1 = TheBank(accountName: 'Dime Dush');
  print('accountBalance of ${user1.accountName} is ${user1.accountBalance}');
  print('accountNumber of ${user1.accountName} is ${user1.accountNumber}');
  user1.deposit(payIn: 2000);
  print(user1.accountBalance);
  user1.withdrawal(payOut: 1000);
  print(user1.accountBalance);
  user1.displayBalance();

  // user2
  final user2 = TheBank(accountName: 'Mike Dean');
  print('accountBalance of ${user2.accountName} is ${user2.accountBalance}');
  print('accountNumber of ${user2.accountName} is ${user2.accountNumber}');
  user1.deposit(payIn: 10000);
  print(user2.accountBalance);
  user1.withdrawal(payOut: 2000);
  print(user2.accountBalance);
  user1.displayBalance();
}

class TheBank {
  final String accountName;
  int? accountNumber;
  double? accountBalance;

  TheBank({
    required this.accountName,
  }) {
    accountNumber = Random().nextInt(1000000000);
    accountBalance = 0.0;
    displayBalance();
  }

  // deposit method use to add money to you balance

  void deposit({double payIn = 0.0}) {
    double newBal = payIn + accountBalance!;
    if (payIn > 0.0) {
      accountBalance = newBal;
      print('Money deposited successfully!');
    } else {
      print('Deposit fail. The lowest deposit is 1.0 Naira');
    }
  }

  void withdrawal({double payOut = 0.0}) {
    double newBal = accountBalance! - payOut;
    if (accountBalance! >= payOut && payOut > 0.0) {
      accountBalance = newBal;
      print('withdrawal succesful');
    } else {
      print("Insufficient funds!");
    }
  }

  void displayBalance() {
    print('Your balance is $accountBalance');
  }
}

my console bank app