Classwork:
Chapter 1: VN 1.1 Introduction to key concepts
Take video notes.
Chapter 1: VN 1.2 Creating and using objects within BlueJ
Chapter 1: VN 1.3 methods and parameters
Assignment:
Using BlueJ’s video notes and source files on edmodo.com, create a new picture where there are more than one person in different locations, a house, a sun and grass.
January 13th, 2015
Classwork:
Using BlueJ’s video notes and source files on edmodo.com, create a new picture where there are more than one person in different locations, a house, a sun and grass.
If you don’t remember exactly how it was done, the video links are on yesterday’s post.
Homework:
6. Implement a class Employee. An employee has a name (a string) and a salary (a double). Write a default constructor, a constructor with two parameters (name and salary), and methods to return the name and salary. Write a small program that tests your class.
OOD – Refresher
Java Video Tutorial 7
Chapter 3: VN 3.1 Fields of class types
Chapter 3: VN 3.2 Constructors and field initialization
Chapter 3: VN 3.3 Solving the 12-hour clock exercise
Homework:
Watch this video:
If you are moving ahead:
Use these libraries, download StdIn.java, StdOut.java, StdDraw.java, and StdAudio.java
Look at Standard output and input.
Redirection and piping.
Standard drawing.
Standard audio.
Graphical user interfaces.
Look at exercises 1 through 9 and work on exercise 10. Submit it to edmodo.com.
Chapter 1: VN 1.4 Solving a challenge exercise
Exercise 1:
Add a sunset to the single-sun version of Picture. That is: make the sun go
down slowly. Remember: The circle has a method slowMoveVertical
that you can use to do this.
Exercise 2: If you added your sunset to the end of the draw
method (so that the sun goes down automatically when the picture is
drawn), change this now. We now want the sunset in a separate method,
so that we can call draw and see the picture with the sun up, and then
call sunset (a separate method!) to make the sun go down.
You will find this code:
private Square wall;
private Square window;
private Triangle roof;
private Circle sun;
You need to add a line here for the second sun,
For example: private Circle sun2;
Then write the appropriate code for creating the second sun.
Exercise 3: Close the picture project, and open the lab-classes project.
This project is a simplified part of a student database designed to keep track of students in laboratory classes and to print class lists.
Create an object of class Student. You will notice that this time you
are not only prompted for a name of the instance, but also for some
other parameters. Fill them in before clicking Ok. (Remember that
parameters of type String must be written in double-quotes.)
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:
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:
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.
Submit your work in edmodo.com
Concepts and terms to know well
A class is like:
A class defines how “objects” or “instances” should be created and maintained.
The “data fields” or “instance fields” define the state of the object.
The “methods” or “behaviors” manipulate the “data fields” or “instance fields” to ensure consistent and proper handling.
If you notice, the instance fields are private. This fact and the use of methods to handle the instance fields promotes ENCAPSULATION.
Unprotected data
Encapsulation
A class that defines an object with instance fields (attributes) and methods(behaviors) is called an ADT: Abstract Data Type
What is an abstraction?
Can you give an example of an abstraction?
“An abstraction is a general concept or idea, rather than something concrete or tangible. In computer science, abstraction has a similar definition. It is a simplified version of something technical, such as a function or an object in a program. The goal of “abstracting” data is to reduce complexity by removing unnecessary information.”
https://techterms.com/definition/abstraction
Implement a class Car_YI with the following properties.
Sample driver/test class:
Car_YI myBeemer = new Car_YI(29); // 29 miles per gallon myBeemer.addGas(20); // tank 20 gallons myBeemer.drive(100); // drive 100 miles System.out.println(myBeemer.getGas()); // print fuel remaining
What to turn in when you submit your work in edmodo.com:
* a. Copy and paste both programs
* b. Attach both files
* c. Output should be included in your tester/driver class as a comment
* d. Test all your code: Think of data that will force execution of all the lines of code.
Classwork:
Write a class SavingsAccount_YI that is similar to the BankAccount class, except that it has an added instance variable interest. Supply a constructor that sets both the initial balance and the interest rate. Supply a method addInterest (with no explicit parameter) that adds interest to the account. Write a tester/driver program that constructs a savings account with an initial balance of $1,000 and interest rate 10%. Then apply the addInterest method five times and print the resulting balance.
/**
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;
}
}
/**
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 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.