/**
   A bank account has a balance that can be changed by 
   deposits and withdrawals.
*/
public class BankAccount {  
	
	private int accountNumber;
	private double balance;
	
   /**
      Constructs a bank account with a zero balance.
   */
   public BankAccount(int anAccountNumber) {   
      accountNumber = anAccountNumber;
      balance = 0;
   }

   /**
      Constructs a bank account with a given balance.
   */
   public BankAccount(int anAccountNumber, double initialBalance) {   
      accountNumber = anAccountNumber;
      balance = initialBalance;
   }

   /**
      Gets the account number of this bank account.
   */
   public int getAccountNumber() {   
      return accountNumber;
   }

   /**
      Deposits money into the bank account.
   */
   public void deposit(double amount) {  
      double newBalance = balance + amount;
      balance = newBalance;
   }

   /**
      Withdraws money from the bank account.
   */
   public void withdraw(double amount) {   
      double newBalance = balance - amount;
      balance = newBalance;
   }

   /**
      Gets the current balance of the bank account.
   */
   public double getBalance() {   
      return balance;
   }   
}