/**
 * A bank account.
 */ 
public class BankAccount {
  
  /** The last name of the account owner. */
  private String lastName;
  
  /** The first name of the account owner. */
  private String firstName;
 
  /** The balance of the account. */
  private double balance;
  
  /** The account number. */
  private int accountNumber;
  
  /**
   * Withdraws the given amount from
   * the bank account.
   * 
   * - The code within the {} is called the
   * method body.
   * - The variable "amount" only exists 
   * within the method withdraw.
   */ 
  public void withdraw(double amount) {
    this.balance = this.balance - amount;
    
    // this is equivalent:
    // this.balance -= amount;
  }
  
  /**
   * Return the balance.
   */
  public double getBalance() {
    return this.balance;
  }
}