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:
- Add a method sayGoodbye to the Greeter class.
- 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.”
- Write a program that constructs a bank account, deposits $1000, withdraws $500, withdraws another $400, and then prints the remaining balance.
- 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:
- Add a method sayGoodbye to the Greeter class.
- 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.”
- Write a program that constructs a bank account, deposits $1000, withdraws $500, withdraws another $400, and then prints the remaining balance.
- 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.
