GreenfootAnIntroductiontoOOP

PresentedbyAdrienneDecker

StephanieHoeppnerFranTrees

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SomematerialsbasedonGreenroomResources.Freetouse,modifyanddistributeunderCreativeCommonsAttributionShareAlike3.0License.

GreenfootGreenfoot

a combination between a framework foracombinationbetweenaframeworkforcreatingtwodimensionalgridassignmentsinJavaandanIDE.

atoolforteachingprogrammingwiththeJavalanguage. Intendedforages14andolder. Downloadfrom:http://www.greenfoot.org/ IthasinterfacetranslationsintolanguagesincludingFrench,GermanandItalian.

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Session DescriptionSessionDescription Inthispresentation,wewillintroduceG fGreenfoot.

ThispresentationisaimedatteachersofintroductoryJavaprogrammingcourses(highschoolsanduniversities)whohaveneverworkedwiththeGreenfoot environmentbefore.

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Presentation DescriptionPresentationDescription Thispresentationisintendedtogiveeducatorsan introduction to the Greenfoot environment aanintroductiontotheGreenfoot environment,ademonstrationofhowitcanbeusedtointroduceobjectorientedprogrammingtostudents,andaj p g g ,guidedapproachtodevelopingGreenfootexperiencesthatcanbeintegratedintoexisting

i lcurricula.

Th i i i ll i d d ll ThesessionispracticallyorientedandallowsparticipantstouseGreenfoot intheirclassroomimmediatelyimmediately.

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SessionGoals

TointroducetheGreenfoot environment Asourcecodeeditor Aclassbrowser Compilationcontrol Execution controlExecutioncontrol

WhilediscussingtheteachingofJava through examples Javathroughexamples

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AgendaAgenda

Building a Greenfoot program (to learn aboutBuildingaGreenfoot program(tolearnaboutGreenfoot)CRABS,WORMS,andLOBSTERS Start with an existing scenario Startwithanexistingscenario IntroduceobjectsandclassesWork with interacting classes Workwithinteractingclasses

LookatmovementintheworldI l d d b h i d d Includerandombehaviorandsound

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AgendaAgenda

Moving beyond the first scenario:Movingbeyondthefirstscenario:DemonstrationofsomeadvancedfeaturesofGreenfoot:Greenfoot: ImagecontrolAnimation Animation

CollisionDetection

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AgendaAgenda

S l i G f t t t h SomeexamplesusingGreenfoot toteachorreviewCStopics

Greenfoot.org PublishingScenarios AvailableResources

Questions?????Q

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Greenfoot (Little Crab Scenario)Greenfoot (LittleCrabScenario)

Like BlueJ Greenfoot teaches objectorientedLikeBlueJ,Greenfoot teachesobject orientedprogramminginavisualmanner.Eachactorisan object that moves around in a world (alsoanobjectthatmovesaroundinaworld(alsoanobject).

Thisallowsteachingofobjectorientedi i l ( h d i i bj )principles(methodinvocation,objectstate)

beforeevenbeginningtolookatorwritedcode.

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Greenfoot EnvironmentGreenfoot Environment

ClassDiagram

World

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Greenfoot classes(HelpOption)

ActorActor GreenfootSoundGreenfootSound

GreenfootGreenfoot MouseInfoMouseInfo

GreenfootImageGreenfootImage WorldWorld

Objects and Classes ClassObjectsandClasses Class Crab

Instance

constructoroftheCrabclass

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Defining state (attributes)Definingstate(attributes)

ObjectInspector

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Defining behavior (methods)Definingbehavior(methods)

Crabmethods

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Defining behavior (methods)Definingbehavior(methods)

MethodsMethodsinheritedfromAnimal

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Definingbehavior(methods)

MethodsMethodsinheritedfromActor

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ActorsActors

'Actors' have predefined state:Actors havepredefinedstate:

image location (in the world)location(intheworld) rotation

CreateanewCrabandpress">Act"Click"Run"tocallactcontinuously

Nothingh !happens!

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LetsinvestigatetheJavacodeforact!

import greenfoot.; // (World, Actor, G f tI d G f t)GreenfootImage, and Greenfoot)

/This class defines a crab. Crabs live on the beach.

/bli l C b t d A i lpublic class Crab extends Animal

{public void act(){

Thecrabdoes{}

}nothingwhenitacts!

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Defining the Crabs behavior for actDefiningtheCrab sbehaviorforactpublic class Crab extends Animal{

public void act(){{

move();}}

} Compile Compile Run Whathappens?

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MovementKey PointMovement KeyPoint

Y h th l l f b t ti / l it Youcanchoosethelevelofabstraction/complexitytoexposetoyourstudentsbypreparingthescenarioscenario.

move();move(); setLocation( getX()+1, getY() );

Defining the Crabs behavior for actDefiningtheCrab sbehaviorfor act Ifcrabisattheedge,turnaroundand

h h

public class Crab extends Animal

gotheotherway.

public class Crab extends Animal{

public void act(){{

move();// more code here

}}

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Ifcrabisattheedge,turnaroundandgo the other waygotheotherway.

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Ifcrabisattheedge,turnsmoothlyandgo the other way!gotheotherway!

public void act(){

()move();if( atWorldEdge() ){{

turn(15);}

}

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ObjectsandClassesl ld h bPopulateyourworldwithcrabs

EachinstanceofaC b has its ownCrab hasitsownattributes(state).

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ObjectsandClasses

Thedescriptionofwhatcomprisesanobject ofaparticulartypeisaclassyp

Aclass definesthebehavior andattributes(characteristics)ofobjects(whatanobjectknowsaboutitself).

Objects areinstances ofaclass.

Crab class: blueprintCrab objects Crab class:blueprintforcrabs

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What a crab knows about itself:Whatacrabknowsaboutitself:

Crabscannotdirectlyaccess:

xyyRotationWorldimage

NeedaccessorsandmutatorsprovidedbyActor to do thatActor todothat.

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Crab inherits from ActorCrab inheritsfromActor Crabscannotdirectly accessdirectlyaccess: x yy Rotation Worldi image

Need accessors andNeedaccessors andmutators providedbyActortodothat.

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Crab inherits from ActorCrab inheritsfromActor Crabscannotdirectly accessdirectlyaccess: x yy Rotation Worldi image

Need accessors andNeedaccessors andmutators providedbyActor todothat.

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Crab inherits from ActorCrab inheritsfromActor Crabscannotdirectly accessdirectlyaccess: x yy Rotation Worldi image

Need accessors andNeedaccessors andmutators providedbyActor todothat.

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Crab inherits from ActorCrab inheritsfromActor Crabs can notCrabscannotdirectlyaccess: x y Rotation WorldWorld image

Needaccessors andmutators providedby Actor to do thatbyActor todothat.

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Objects and ClassesObjectsandClasses Populateyourworldwithafewinstancesofthep yCrab class.

Cantherebemorethanoneobjectinaposition? CanaCrabmovetoapositionthatanotherCrab occupies?

Can a Crabmove outside the boundaries of the CanaCrabmoveoutsidetheboundariesoftheworld?

HowisinvokingtheactmethodofaCrab gdifferentfromclickingtheact executioncontrolbutton.

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Populatingtheworld(U i th G f t API)(UsingtheGreenfoot API)http://www.greenfoot.org/doc/javadoc/

public CrabWorld() {

super(560, 560, 1);

addObject(new Crab() 100 200);addObject(new Crab(), 100,200);addObject(new Crab(), 150,290);addObject(new Crab(), 300,400);addObject(new Crab(), 500,50);

}}

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SavetheWorld!

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Interactingclassesh b hThecrabsarehungry!

Crabseatworms.C abs eat o s.1. RightclickAnimal;choose"New Subclass..."2 Name it "Worm"2. Nameit"Worm".

3. Chooseanimage.

Addwormstoyourworld.

RunWhathappens?pp

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ModifytheCrabclasstoteachthecrabtoeatworms.

If the crab sees a worm Worm.classIfthecrabseesaworm Eattheworm

Worm.class

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ModifytheCrabclasstoteachthecrabtoeatworms

If the crab sees a wormIfthecrabseesaworm Eattheworm public void act()

{{move();if(canSee(Worm.class)){{

eat(Worm.class);}else if( atWorldEdge() )else if( atWorldEdge() ){

turn(15);}

}37

Greenfoot soundsGreenfoot soundsif(canSee(Worm.class)){{

eat(Worm.class);G f t l S d(" l ")Greenfoot.playSound("slurp.wav");

}Y h h l l f Youcanchoosethelevelofabstraction/complexitytoexposetoyour

d b i h istudentsbypreparingthescenario. Animal definescanSeeandeat...

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...butitdoesnothaveto.

Summary: so far..Summary:sofar..

The difference between objects and classes Thedifferencebetweenobjectsandclasses Methodsignatureanddefinition Parameters Booleanexpressions int,boolean,andvoid returns private vs public private vs public if;if-else

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More interesting behaviorMoreinterestingbehavior

Random NumbersRandomNumbers InGreenfoot:

int r = Greenfoot.getRandomNumber(100);g ( ); Returnsarandomint between0(inclusive)and100(exclusive)

int r Greenfoot getRandomNumber(100) 50; int r = Greenfoot.getRandomNumber(100)- 50; Returnsarandomint between50(inclusive)and50(exclusive)

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A more interesting CrabAmoreinterestingCrabpublic class Crab extends Animal{{

public void act(){

if ( atWorldEdge( ) ){

(1 )turn(15);} move();if (canSee(Worm.class)){{

eat(Worm.class); }// Generate a random int between 0 and 100// If the number is less than 10, turn a random number of degrees // between 0 and 45 (right or left).

}}

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The improved CrabTheimprovedCrabpublic class Crab extends Animal{

public void act(){{

turnAtEdge()randomTurn();move();lookForWorm();

}}}

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An alternate CrabWorldAnalternateCrabWorldpublic CrabWorld() {

super(560, 560, 1); populateWithCrabs();populateWithWorms();

}public void populateWithCrabs(){

final int NUM_CRABS = //add NUM_CRABS crabs in random locations

} public void populateWithWorms(){

final int NUM_WORMS = //add NUM_WORMS worms in random locations

} 43

Gameisoverwhentherearenoworms!

Whose responsibility is it to keep track of theWhoseresponsibilityisittokeeptrackoftheworms?

World Methods? WorldMethods? Howdowe"stop"theGREENFOOTGame?

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BoringBoring

NothingEXCITINGhappens! Introduce

TheLobster

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InteractiveprogramsTh L b h bTheLobstermeetsthecrab

Crabseatworms. Lobsterseatcrabs! Yougettocontrolthesinglecrab!

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The LobsterTheLobster

TheLobster behaveslikethecrabdidbuteatse obste be a es e t e c ab d d but eatscrabsinsteadofworms.

public void act(){

turnAtEdge();randomTurn();move();lookForCrab();

}}

The crab's behavior will changeThecrab sbehaviorwillchange.

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The interactive CrabTheinteractiveCrab

The crab is controlled by the keyboardThecrabiscontrolledbythekeyboard. Leftarrowturnthecrab4degreesRight arrow turns the crab 4 degrees Rightarrowturnsthecrab4 degrees

public void act()public void act(){

checkKeypress();move();lookForWorm();

}

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KeypressKeypress

public void checkKeypress()public void checkKeypress(){

if (Greenfoot.isKeyDown("left")) {

turn(-4);}}if (Greenfoot.isKeyDown("right")) {

turn(4);turn(4);}

}

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Animatedcreaturesh bAnimatethecrab!

The image files used for your animationTheimagefilesusedforyouranimationshouldliveintheimagesfolderfortheprojectproject. crab.pngcrab2 png crab2.png

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Animate the crab!Animatethecrab!private GreenfootImage image1;p g gprivate GreenfootImage image2;

public Crab(){

iimage1 = new GreenfootImage("crab.png");image2 = new GreenfootImage("crab2.png");setImage(image1);setImage(image1);

}

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Animate the crab!Animatethecrab!

public void act()public void act(){

checkKeypress();checkKeypress();move();lookForWorm();lookForWorm();switchImage();

}}

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OurnewWorld

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GameisoverwhentherearenowormsORwhenalobstereatsthe

crab

DistinguishbetweenWINandLOSS

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(Some) Advanced Features(Some)AdvancedFeatures

CollisionDetection&Animations

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Key Point (Reiterated)KeyPoint(Reiterated)

You can control the level of abstraction for theYoucancontrolthelevelofabstractionforthestudentswithregardstomovementandanimationanimation.

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Moving ActorsMovingActorspublic void move(double distance) {double angle = Math.toRadians( getRotation() );

int x=(int)Math.round(getX()+Math.cos(angle) distance);int x (int)Math.round(getX()+Math.cos(angle) distance);int y=(int)Math.round(getY()+Math.sin(angle) distance);

i ( )setLocation(x, y);}

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Motion Using VectorsMotionUsingVectors

SmoothMover class uses a Vector to holdSmoothMover classusesaVector toholddirectionandspeedofmotion.

Can create subclasses of SmoothMover to CancreatesubclassesofSmoothMover tousethisstyleofmotion.C ill h i f d l d Canillustratetheseparationofmodelandview.

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Collision DetectionCollisionDetection

Even if you dont have the students controlEvenifyoudon thavethestudentscontrolmotion/turning/etc.youcanstillhavethemwrite more sophisticated collision detectionwritemoresophisticatedcollisiondetectionbehaviorsusingthebuiltinmethodsinActorActor.

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Collision Detection MethodsCollisionDetectionMethodsjava.util.List getIntersectingObjects(java.lang.Class cls)

java.util.List getNeighbours(int distance,boolean diagonal,java.lang.Class cls)

java.util.List getObjectsAtOffset(int dx,int dy,java.lang.Class cls)

j il i Obj (i di j l Cl l )java.util.List getObjectsInRange(int radius,java.lang.Class cls)

ActorgetOneIntersectingObject(java.lang.Class cls)

ActorgetOneObjectAtOffset(int dx,int dy,java.lang.Class cls)

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getOneIntersectingObject(java.lang.Class cls) g g j (j g )

Pass in the class of the object to look for a particularPassintheclassoftheobjecttolookforaparticulartypeofcollision

Passinnull tolookforanyintersectingobjecty g j

Returns one Actor object that matches the criteria.ReturnsoneActor objectthatmatchesthecriteria. null isreturnedifnointersectionsaredetected

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getOneObjectAtOffset(i t d i t d j l Cl l )(int dx, int dy, java.lang.Class cls)

L k l h f bj t ( i d d d ) Lookelsewhereforanobject(passinadxanddy) TheClassparameterworksthesameasprevious.

Returnssameasprevious:anActor objectthatisll if i t ti d t t dnull ifnointersectionsaredetected.

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getIntersectingObjects(java.lang.Class cls)g g j (j g )

Returns a list (java.util.List) of allReturnsalist(java.util.List)ofallintersectingobjectsofaparticularclasstypecls. Passinginnull returnsintersectionsofalltypes.g yp

Can be used to discuss collections, generics, foreachCanbeusedtodiscusscollections,generics,for eachloop.

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getObjectsAtOffset(int dx int dy(int dx, int dy,

java.lang.Class cls)

Analogous to getObjectAtOffset except that it AnalogoustogetObjectAtOffset exceptthatitreturnsalloftheobjectsthatareintersecting.

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getObjectsInRangeg j g

List getObjectsInRange(int r, java lang Class cls)

ll l

List getObjectsInRange(int r, java.lang.Class cls)Return all objects within range 'r' around this object.

cell:10pixels

An object is "in jrange" if its center point is inside theinside the circle.

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r=6(cells)

getNeighboursg g

Most useful in a world where actors areMostusefulinaworldwhereactorsarecontainedinacell(likeGridWorld casestudyfor AP CS Exam)forAPCSExam).

Returnsthelistofneighborsinthefourcardinal directions distance cells awaycardinaldirectionsdistance cellsawayfromtheactorscurrentlocation.P i h b l Passingtrue totheboolean parameterincludesthediagonals.

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GreenfootImageGreenfootImage

This is the class that represents the images ofThisistheclassthatrepresentstheimagesoftheactorsandtheworldinthescenarios.

You can programmatically manipulate these Youcanprogrammaticallymanipulatetheseimagesordrawyourownimagesprogrammaticallyprogrammatically.

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Drawing MethodsDrawingMethodsclear()

drawImage(GreenfootImage image int x int y)drawImage(GreenfootImage image,int x,int y)

drawLine(int x1,int y1,int x2,int y2)

drawOval(int x int y int width int height)drawOval(int x,int y,int width,int height)

drawPolygon(int[] xPoints,int[] yPoints,int nPoints)

drawRect(int x, int y, int width, int height)

OutlineShapes

drawRect(int x,int y,int width,int height)

drawShape(java.awt.Shape shape)

fill()

Setsthecurrentdrawingcolor.

Needs to be done()

fillOval(int x,int y,int width,int height)

fillPolygon(int[] xPoints,int[] yPoints,int nPoints)

FilledinShapes

Needstobedonebeforedrawingor

filling.yg y

fillRect(int x,int y,int width,int height)

fillShape(java.awt.Shape shape)68

Sidenote: Drawing TextSidenote:DrawingText

drawString(java.lang.String string, int x, int y)drawString(java.lang.String string,int x,int y) Drawthetextgivenbythespecifiedstring,usingthecurrentfontandcolor.

java.awt.Font getFont() Getthecurrentfont.

setColor(java.awt.Color color) Setthecurrentdrawingcolor.g

setFont(java.awt.Font f) Setthecurrentfont.Set the current font.

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Growing, Shrinking, TransparencyGrowing,Shrinking,Transparencyint getHeight()

Return the height of the imageReturntheheightoftheimage.int getWidth()

Returnthewidthoftheimage.scale(int width,int height)

Growing&

Shrinking

Scalesthisimagetoanewsize.

int getTransparency()Return the current transparency of the image.Returnthecurrenttransparencyoftheimage.

setTransparency(int t)Setthetransparencyoftheimage.

mirrorHorizontally()mirrorHorizontally()Mirrorstheimagehorizontally(fliparoundthexaxis).

mirrorVertically()Mirrorstheimagevertically(fliparoundtheyaxis).

Otheranimated

rotate(int degrees)Rotatesthisimagearoundthecenter. 70

effects

Fun with ImagesFunwithImages

Useful if interested in using some of the mediaUsefulifinterestedinusingsomeofthemediacomputationstuff

See getColorAt(x,y) and setColorAt(x,y)SeegetColorAt(x,y)andsetColorAt(x,y)methods Grayscale animagey g Filtersonimages Createnegative Chromakey

Canbeusedtoreinforceloopsp

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GreenfootGreenfoot

SimpleAssignmentswith Dice and CardswithDiceandCards

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BooleanExpressions:CrapsThegameconsistsofrolling26sideddice.Theshootermakesa"comeoutroll"withtheintentionofestablishingapoint.If the shooter's comeout roll is a 2 3 or 12 it is called "craps" (theIftheshooter scomeoutrollisa2,3or12,itiscalled craps (theshooterissaidto"crapout")andtheroundendswithplayerslosing.

Acomeoutrollof7or11iscalleda"natural,"resultinginawin.

If the shooter's comeout roll is a 4 5 6 8 9 or 10 this number becomesIftheshooter scomeoutrollisa4,5,6,8,9,or10,thisnumberbecomesthe"point".Oncethe"point"isestablished,theshooterwillnowcontinuerollingforeitherthepointnumberoraseven.

If th h t i f l i lli th i t b th lt i iIftheshooterissuccessfulinrollingthepointnumber,theresultisawin.Iftheshooterrollsaseven(calleda"sevenout"),theresultisaloss.

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BooleanExpressions:Craps

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Arrays and ArrayLists: Poker (part 1)ArraysandArrayLists:Poker(part1)

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Interfaces: Poker (Part2)Interfaces:Poker(Part2)

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Interfaces: Poker (Part2)Interfaces:Poker(Part2)publicinterfaceIHandPropertyTester{{/***Returnstrueifandonlyifhandsatisfiesthisproperty*@param handisthehandtestedp*@returntrueifhandsatisfiespropertybeingtested*/boolean hasProperty(Handhand);

/***Returnsthevalueofthishandifhandsatisfiestheproperty*@param handisthehandtested*@returnvalueofthehandtested.*/int getHighValue(Handhand);

}}

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Arrays and 2D arraysArraysand2 Darrays

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StudentLottery( h h )(Whogetsthisquestionorprize?)

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BeyondAdvanced(andontoreally,reallycool)

GamePads,Kinect

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Game PadsGamePads

PS2 and XBox like game padsPS2andXBox likegamepads Supportclassesneededandavailable(alongwith documentation and examples)withdocumentationandexamples)

http://www.greenfoot.org/doc/gamepad/

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KinectKinect

http://www greenfoot org/doc/kinect/http://www.greenfoot.org/doc/kinect/ Kinect video

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Crabs,andLobsters,andBearsohmy!?!

Help,Resources,&Community

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Greenfoot GalleryGreenfootGallery

Share!Share!

Greenroom

Meet!

More informationMoreinformation www.greenfoot.org

discussiongroup

scenariorepositoryp y

tutorials(textandvideo)

Greenfoot GalleryGreenfoot Gallery

Greenroom

Adrienne: newyork hub@greenfoot org Adrienne:newyorkhub@greenfoot.org

Fran:newjerseyhub@greenfoot.org

Questions?Questions?

DiscussionTime

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