Announcements Announcements Reading for Wednesday Reading for - - PowerPoint PPT Presentation

Announcements Announcements

• Reading for Wednesday

Reading for Wednesday

– the rest of Chapter 2 (with a few exceptions) Check – Check http://www.itk.ilstu.edu/faculty/kwsuh/courses/ ITK168/Fall2011/index.htm ITK168/Fall2011/index.htm – http://www.itk.ilstu.edu/itk168

• Quiz
• Quiz

Object-oriented vs. non-OO programming

• Demo

Demo

Software Objects Software Objects

• Maintain information called attributes

Maintain information called attributes

• Answer questions based on that

information using queries information using queries

• Change the information using commands
• Queries and commands are collectively

called services

• Services are provided to clients

Objects Objects

• Based on a “template” called a class

Based on a template called a class

• Have the same attributes and services

Att ib t h diff t l

• Attributes have different values
• Services are the same for all objects of the

same class

Class Definitions Class Definitions

• This is what we code in a Java program

This is what we code in a Java program

• Used to create multiple objects

C ll d i t f th l – Called instances of the class

• Specifies attributes and services
• Class – vs – Object

– Blueprint – house p – Pattern – dress – Cookie cutter - cookie

Queries and Attributes Queries and Attributes

• A query is always answered by the object

A query is always answered by the object

– True or false A number – A number – A string of characters

A b d th bj t’

• Answers are based on the object’s

attributes (therefore possible questions li it d) are limited)

Commands Commands

• Change the value of an attribute (or

Change the value of an attribute (or attributes) to reflect a new reality

• Can be visualized using a state of
• Can be visualized using a state of

change diagram

St t f th bj t b f – State of the object before – State of the object after

Class Diagram Class Diagram

• Rectangle with 3 sections

Rectangle with 3 sections

– Name of class List of attributes – List of attributes – List of services

• Sometimes class diagrams do not list the

attributes

– Black-box programming

Modeling Robots Modeling Robots

• Book author provides many classes in a

Book author provides many classes in a package called – becker.jar

• Basic enough to grasp easily
• Basic enough to grasp easily
• Complex enough to be interesting
• Simple enough to be easy to program
• Rich enough to demonstrate OOP

g concepts

Incomplete Class Diagram Incomplete Class Diagram

Robot

• street: int
• avenue : int
• direction: Direction
• backpack: ThingBag

+ Robot(City aCity, int aStreet, int anAvenue, Direction aDirection) + move(): void t L ft() id + turnLeft(): void + pickThing(): void + putThing(): void + putThing(): void

Class Details Class Details

• Attributes

Al i t ( ) – Always private (-) – Name – Type

• Constructors

Constructors

– Always public (+) – Used to build objects – No return type S th l – Same name as the class – May or may not have parameter list

• Default constructor
• Special constructor
• Services

– Public (+), private (-), or protected (#) – Name Parameter list – Parameter list – Return type

Services Services

• A robot performs a service only when it is

p y invoked by a corresponding message

– turnLeft – turns 90 degrees to the left remaining on the same intersection the same intersection

• Turning is a safe activity

– move – attempts to move forward one intersection still facing in the same direction – pickThing – attempts to pick up a thing from the current intersection – putThing – attempts to put a thing down in the current intersection

• Moving picking up and putting down objects are not always
• Moving, picking up, and putting down objects are not always

safe activities

Messages Messages

Argument list “dot” Argument list aka: parameter list

karel.move();

semicolon Reference to the

• bject

The service to execute semicolon j aka: variable aka: method

Example Program Example Program

• Situation

Situation

– A delivery robot is to pick up a parcel, represented by a Thing at intersection (1 2) represented by a Thing, at intersection (1,2) and deliver it to (2,3) Initial state Final state

The Java Program The Java Program

import becker.robots.*; public class DeliverParcel { pub c c ass e e a ce { public static void main(String[] args) { //Set up the initial situation City prague = new City(); Thing parcel = new Thing(prague, 1, 2); g p g(p g , , ); Robot karel = new Robot(prague, 1, 0, Direction.EAST); //Direct the robot to the final situation karel.move(); (); karel.move(); karel.pickThing(); karel.move(); karel.turnLeft(); //start turning right as 3 lefts (); // g g karel.turnLeft(); karel.turnLeft(); //finished turning right karel.move(); karel.putThing(); p g(); karel.move(); } }

Sketch the initial state and final state of this program

import becker.robots.*; public class GoAroundRoadBlock p { public static void main(String[] args) { //set up initial situation City ny = new City(); Wall blockAve0 = new Wall(ny, 0, 2, Direction.WEST); ll bl k 1 ll( 1 2 i i ) Wall blockAve1 = new Wall(ny, 1, 2, Direction.WEST); Robot mark = new Robot(ny, 0, 2, Direction.WEST); Robot ann = new Robot(ny, 0, 1, Direction.EAST); //what does mark do here? mark turnLeft(); mark.turnLeft(); mark.move(); mark.move(); mark.turnLeft(); mark.turnLeft(); mark.turnLeft(); mark.move(); //what does ann do here? ann.turnLeft(); ann.turnLeft(); t L ft() ann.turnLeft(); ann.move(); ann.move(); ann.turnLeft(); } }

Reading Documentation Reading Documentation

• www.learningwithrobots.com

– www.learningwithrobots.com/doc/index.html

• http://download.oracle.com/javase/6/docs/api/ or
• http://download.oracle.com/javase/7/docs/api/

p j p

Basic Java Patterns Basic Java Patterns

• Java Program Pattern

Java Program Pattern

• Object Instantiation Pattern

C d I ti P tt

• Command Invocation Pattern
• Sequential Execution Pattern

Planting Flowers

• You have a square enclosure. You want to

have a robot plant flowers (Things) around the enclosure See below the enclosure. See below. Questions: Ho man alls are there? Ho are the positioned? How many walls are there? How are they positioned? Where do the flowers come from?

Beyond Robots Beyond Robots

• Objects are used in all contexts in Java

Objects are used in all contexts in Java programs.

• The same patterns are used to develop
• The same patterns are used to develop

GUI (Graphical user interface) programs as to develop Robot programs as to develop Robot programs.

• However, the classes we use are different.

Sample Simple GUI

• Use the JFrame, JLabel, JTextField, and

JTextArea classes to produce a program that g creates a window that looks like a browser window (sort of).

End of Chapter End of Chapter

• Be sure to study the patterns listed at the

Be sure to study the patterns listed at the end of each chapter

• You will be expected to understand them
• You will be expected to understand them
• Likewise, study the concept map at the

d f h h t end of each chapter

• Download and complete the exercise set

posted on the course web site

Extending Classes with Services Extending Classes with Services IT 168 Fall 2011

Robots Learning to Program with Java Learning to Program with Java Byron Weber Becker

h chapter 2

Chapter 2 objectives Chapter 2 objectives

• Extend an existing class with new

Extend an existing class with new commands

• Explain how a message sent to an object
• Explain how a message sent to an object

is resolved to a particular method U i h it d i

• Use inherited services
• Override services in the superclass
• Java programming convention

Sketch Before and After Sketch Before and After

import becker.robots.*; public class Longer p g { public static void main(String[] args) { City austin = new City(); Robot lisa = new Robot(austin, 3, 2, Direction.EAST); li () lisa.move(); lisa.move(); lisa.move(); lisa.turnLeft(); lisa.turnLeft(); lisa turnLeft(); lisa.turnLeft(); lisa.move(); lisa.move(); lisa.move(); lisa.turnLeft(); lisa.turnLeft(); lisa.move(); lisa.move(); lisa.move(); lisa.turnLeft(); lisa.move(); li () lisa.move(); lisa.move(); lisa.turnLeft(); lisa.turnLeft(); } }

Robot vs ExperimentalRobot Robot vs ExperimentalRobot

Robot

Experimental Robot

• street:int
• avenue:int
• direction:Direction
• packpack:ThingBag

Robot

• street:int
• avenue:int
• direction:Direction
• packpack:ThingBag

+ Robot(City aCity, int aStreet, int anAvenue, Direction aDirection) + mo e()

• id

+ ExperimentalRobot(City aCity, int aStreet, int anAvenue, Direction aDirection) + mo e()

• id

+ move():void + turnLeft():void + pickThing():void + putThing():void + move():void + move3():void + turnLeft():void + turnRight():void + putThing():void + turnRight():void + turnAround():void + pickThing():void + putThing():void + putThing():void

Sketch Before and After Sketch Before and After

import becker.robots.*; public class Shorter { public static void main(String[] args) p ( g[] g ) { City austin = new City(); ExperimentalRobot lisa = new ExperimentalRobot(austin, 3, 2, Direction.SOUTH); lisa.move3(); lisa.turnRight(); lisa.move3(); lisa.turnAround(); lisa.move3(); lisa.turnLeft(); lisa.move3(); (); lisa.turnAround(); } }

Abstraction Abstraction

• Raising the level of abstraction creates a

Raising the level of abstraction creates a more natural programming language

Makes programs easier to write – Makes programs easier to write – Allows us to understand programs better Makes programs easier to debug – Makes programs easier to debug – Makes programs easier to modify C t bl d – Creates reusable code

Vocabulary Vocabulary

• Extends or inherits

Extends or inherits

• Superclass or parent class

S b l hild l

• Subclass or child class
• Superclasses (plural) Grandparent or

great-grandparent

• In a class diagram the Superclass is

g p shown above the subclass with arrow pointing from subclass to superclass p g p

• This represents an “IS-A” relationship

Extending Robot Extending Robot

Robot

• street:int
• avenue:int
• avenue:int
• direction:Direction
• packpack:ThingBag

+ Robot(City aCity, int aStreet, int anAvenue, Direction aDirection) + move():void + turnLeft():void + pickThing():void + putThing():void

E i t lR b t ExperimentalRobot

+ ExperimentalRobot(City aCity, int aStreet, int anAvenue, Direction aDirection) + turnAround():void + turnRigth():void + move3():void

Form of an Extended Class Form of an Extended Class

import <<importedPackage>>; public class <<ClassName>> extends <<SuperClass>> { <<list of attributes used by this class>> <<list of attributes used by this class>> <<list of constructors for this class>> <<list of services provided by this class>> }

Constructor of Subclass Constructor of Subclass

public ExperimentRobot(City theCity, int street, int avenue, Direction aDirection) { super(theCity, street, avenue, aDirection); }

• super refers to the superclass

– In this case Robot

this this

• Every method has at least one automatic

Every method has at least one automatic parameter

The calling object – The calling object – Not passed in the parameter list

Inside a method thi represents the

• Inside a method, this represents the

calling object // move the calling object this.move();

Subclass Methods Subclass Methods

• turnAround()

turnAround()

• move3()

t Ri ht()

• turnRight()

Flow of a Java Program Flow of a Java Program

• Write a main method to declare an

Write a main method to declare an ExperimentalRobot and do the following:

Move one block – Move one block – Turn around Move 3 blocks – Move 3 blocks – Turn left M t bl k – Move two blocks – Turn right

Extension vs Modification Extension vs Modification

• The Robot class was created by the

The Robot class was created by the author and only the compiled class (byte code) is shared code) is shared

– The Robot class is closed for modification

The Robot class is programmed in a way

• The Robot class is programmed in a way

to allow users to extend the class

Th R b t l i f t i – The Robot class is open for extension

The Thing Class The Thing Class

• Explore the documentation

– http://www.learningwithrobots.com/doc/index.html

• Change the appearance of a Thing

Thing deceptiveThing = new Thing(aCity, 3, 4); WallIcon anIcon = new WallIcon(); deceptiveThing.setIcon(anIcon);

In Sec2.3 you are asked to Complete this Cl Class

import becker.robots.*; public class Lamp extends Thing{ public Lamp(City myCity int street int ave) { public Lamp(City myCity, int street, int ave) { … } public void turnOn() { … } public void turnOff() { … } }

The Constructor The Constructor

• Call to super

Call to super

• Might add additional information
• A street light is off during the day and on

at night – you need to decide which should be default

• Code it

Code it

The Lamp Class The Lamp Class

• What does a Thing look like?

What does a Thing look like?

• What should a Lamp look like?

Wh t h ld b th diff b t

• What should be the difference between a

Lamp that is on and one that is off?

• How do you change the appearance of a

Thing?

Creating a Color Object Creating a Color Object

• public Color(int r int g int b int a)

public Color(int r, int g, int b, int a)

– Creates an sRGB color with the specified red, green blue and alpha values in the range (0 - green, blue, and alpha values in the range (0 255). – Parameters: Parameters:

• r - the red component
• g - the green component
• b - the blue component
• a - the alpha component

Color onColor = new Color(255, 255, 200, 150);

Is the Lamp On or Off? Is the Lamp On or Off?

public void turnOn() { Color onColor = new Color(255, 255, 200, 150); CircleIcon onIcon = new CircleIcon(onColor); this.setIcon(onIcon); }

• How would the turnOff method differ?
• How would the turnOff method differ?

The Lamp Class The Lamp Class

import java.awt.Color; import becker robots *; import becker.robots. ; import becker.robots.icons.CircleIcon; public class Lamp extends Thing{ public Lamp(City myCity, int ave, int street) { super(myCity, ave, street); this.turnOff(); } public void turnOn() { Color onColor = new Color(255, 255, 200, 150); CircleIcon onIcon = new CircleIcon(onColor); this.setIcon(onIcon); } public void turnOff() { Color offColor = new Color(0, 0, 0); CircleIcon offIcon = new CircleIcon(offColor, .25); this.setIcon(offIcon); } }

Testing the Lamp Class Testing the Lamp Class

import becker.robots.*; public class LampTest { p p { public static void main(String[] args) { // set up city City myCity = new City(); Lamp lamp1 = new Lamp(myCity, 1, 0); Lamp lamp2 = new Lamp(myCity, 1, 1); hi d hi ( i 1 2) Thing dot = new Thing(myCity, 1, 2); SERobot karl = new SERobot(myCity, 0, 0, Direction.EAST); // turn one lamp on the other off lamp1.turnOn(); lamp2.turnOff(); // pick up one lamp // pick up one lamp karl.turnRight(); karl.move(); karl.pickThing(); // place on next lamp karl.turnLeft(); karl.move(); karl.putThing(); // pick up thing karl.move(); karl.pickThing(); // t thi l // put thing on lamp karl.turnAround(); karl.move(); karl.putThing(); } }

Programming Style Programming Style

• Whitespace

p

• Indentation
• Naming conventions

P k – Packages – Classes – Methods – Variables – Constants

• Comments
• Comments

– Single line – Multi-line – Javadoc

Closed for Modification Closed for Modification

• How can I change the Robot methods

How can I change the Robot methods

– move, turnLeft, etc

Suppose I want to create a Flying Robot

• Suppose I want to create a Flying Robot

– One that moves very quickly – What changes might I make

Overriding the move Method Overriding the move Method

• The speed of a Robot is the number of moves it

The speed of a Robot is the number of moves it makes in one second

• The default value of a Robot’s speed is 2

p

• This can be changed by using this Robot

method

public void setSpeed(double movesPerSecond)

• Override the move method for our FlyingBot so it

tra els 20 blocks per second travels 20 blocks per second

• We want the robot to turn at a normal speed so

you must reset the speed to default at the end of you must reset the speed to default at the end of the move method

FlyingBot that Walks FlyingBot that Walks

• My FlyingBot typically flies but

My FlyingBot typically flies, but

• ccasionally it might want to walk a few

blocks (just for exercise) blocks (just for exercise)

• Write a walk method that moves at the

default speed default speed

• What happens if we do not reset the

speed in the overridden move method

Redesigning the FlyingBot Redesigning the FlyingBot

• How quickly will our FlyingBot turn

How quickly will our FlyingBot turn

• I’ve changed my mind. I want the

FlyingBot to do everything fast (as a FlyingBot to do everything fast (as a default setting) and only slow down if I choose to call a slower method choose to call a slower method

– walk t Sl – turnSlow

• How would my design change

Redesigning PlantingFlowers Redesigning PlantingFlowers

• Change the PlantingFlowers practice

Change the PlantingFlowers practice exercise from the chapter 1 slides to use a

Garden class that extends City and starts out – Garden class that extends City and starts out with the walls already created – GardenerBot class that extends RobotSE GardenerBot class that extends RobotSE

• Automatically start the Robot at (0,1) facing south
• Automatically start the Robot with enough flowers

y g to complete the garden

ColorBot ColorBot

• Create a RobotSE that draws attention to

Create a RobotSE that draws attention to itself by changing color when it moves

• Typically the ColorBot will be red (like all
• Typically the ColorBot will be red (like all

Robots), but when the ColorBot moves it should change color (you choose a color) should change color (you choose a color)

• Write a main method to test the ColorBot

l class