An ADT: Greeter

public class Greeter
{
   public String sayHello()
   {
      String message = "Hello, World!";
      return message;
   }
}

The tester class also called the driver:

public class GreeterTest
{
   public static void main(String[] args)
   {
      Greeter worldGreeter = new Greeter();
      System.out.println(worldGreeter.sayHello());
   }
}

An ADT: BankAccount

/**
   A bank account has a balance that can be changed by 
   deposits and withdrawals.
*/
public class BankAccount
{  
   private double balance;

   /**
      Constructs a bank account with a zero balance.
   */
   public BankAccount()
   {   
      balance = 0;
   }

   /**
      Constructs a bank account with a given balance.
      @param initialBalance the initial balance
   */
   public BankAccount(double initialBalance)
   {   
      balance = initialBalance;
   }

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

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

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

The driver class:

/**
   A class to test the BankAccount class.
*/
public class BankAccountTester
{
   /**
      Tests the methods of the BankAccount class.
      @param args not used
   */
   public static void main(String[] args)
   {
      BankAccount harrysChecking = new BankAccount();
      harrysChecking.deposit(2000);
      harrysChecking.withdraw(500);
      System.out.println(harrysChecking.getBalance());
      System.out.println("Expected: 1500");      
   }
}

Classwork:

1. Add a method sayGoodbye to the Greeter class.
2. Add a method refuseHelp to the Greeter class. It should return a string such as “I am sorry, Dave. I am afraid I can’t do that.”
3. Write a program that constructs a bank account, deposits $1000, withdraws $500, withdraws another $400, and then prints the remaining balance.
4. Add a method

void addInterest(double rate)

to the BankAccount class that adds interest at the given rate. For example, after the statemetns

BankAccount momsSavings = new BankAccount(1000);
momsSavings.addInterest(10); // 10% interest

the balance in momsSavings is $1,100.

Assignments:

1. Add a method sayGoodbye to the Greeter class.
2. Add a method refuseHelp to the Greeter class. It should return a string such as “I am sorry, Dave. I am afraid I can’t do that.”
3. Write a program that constructs a bank account, deposits $1000, withdraws $500, withdraws another $400, and then prints the remaining balance.
4. Add a method

void addInterest(double rate)

to the BankAccount class that adds interest at the given rate. For example, after the statemetns

BankAccount momsSavings = new BankAccount(1000);
momsSavings.addInterest(10); // 10% interest

the balance in momsSavings is $1,100.