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Housekeeping material
  • Module name: Slick0220: Simulating a pandemic
  • File: Slick0220.htm
  • Published: 02/07/13
  • Revised: 06/11/15 for 64-bit
  • Revised: 10/03/15
Disclaimers:

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

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In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.

Complete program listing

Complete listings of the code discussed in this module are provided in Listing 8 and Listing 9 .

Listing 8 . Source code for Slick0220.
/*Slick0220.java Copyright 2013, R.G.BaldwinThis program simulates the propagation of a fatal communicable disease within a population.A single infected sprite is introduced into a large population of sprites. The disease is spread by physicalcontact with an infected sprite. You can watch as the disease either spreads and kills theentire population or spreads for awhile, then recedes and dies out. Infected sprites are colored red. Healthysprites are colored green. A sound is emitted (for drama) each time there is contact between an infected sprite anda healthy sprite. The final outcome is determined both by chance and byseveral factors including: -The maximum life expectancy of an infected sprite-The maximum probability of infection due to contact with an infected sprite-The maximum degree of mobility of both infected and healthy sprites-The population density of sprites. The actual values for the first three factors for eachindividual are determined by the maximum value multiplied by a random number between 0 and 1.0.Instance variables are provided for each of these factors. You can modify the values and recompile the program toexperiment with different combinations of the factors. A good exercise for a student would be to create a GUIthat allows the factors to be entered more easily for purposes of experimentation.Tested using JDK 1.7 under WinXP *********************************************************/import org.newdawn.slick.AppGameContainer; import org.newdawn.slick.BasicGame;import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics;import org.newdawn.slick.Image; import org.newdawn.slick.SlickException;import org.newdawn.slick.Color; import org.newdawn.slick.Sound;import java.util.Random; import java.util.ArrayList;import java.util.Iterator; public class Slick0220 extends BasicGame{//The values of the following variables can be changed// to effect the spread of the disease.//Set the life expectancy of an infected sprite // in frames.int infectedSpriteLife = 96;//Set the maximum fraction of exposed sprites that will // become infected.float probabilityOfInfection = 0.5f;//Set the maximum step size that a sprite will move in // one frame.float maxStepSize = 1;//Set the initial number of sprites in the population. int numberSprites = 1000;//References to Sprite01 objects are stored here.ArrayList<Sprite01>sprites = new ArrayList<Sprite01>();//These variables are populated with references to Image // objects later.Image redBallImage; Image greenBallImage;//This variable is populated with a reference to a Sound// object later. Sound blaster;//These variables are populated with information about// the background image later. Image background = null;float backgroundWidth; float backgroundHeight;//This object is used to produce random values for a// variety of purposes. Random random = new Random();//This is the frame rate we would like to see and// the maximum frame rate we will allow. int targetFPS = 24;//----------------------------------------------------// public Slick0220(){//constructor//Set the title super("Slick0220, baldwin");}//end constructor //----------------------------------------------------//public static void main(String[] args)throws SlickException{ AppGameContainer app = new AppGameContainer(new Slick0220(),500,500,false); app.start();}//end main //----------------------------------------------------//@Override public void init(GameContainer gc)throws SlickException { //Create Image objects that will be used to visually// represent the sprites. redBallImage = new Image("redball.png");greenBallImage = new Image("greenball.png");//Create a Sound object. blaster = new Sound("blaster.wav");//Create a background image and save information // about it.background = new Image("background01.jpg"); backgroundWidth = background.getWidth();backgroundHeight = background.getHeight();//Add a red sprite as the first element in the // ArrayList object. This sprite carries the disease// into the population. //Put it in the center of the game window. Make the// direction of motion random. Make the speed of // motion (step size)random. Make the size random.// Specify a white (do nothing)color filter. sprites.add(new Sprite01( redBallImage,//imagebackgroundWidth/2.0f,//initial position backgroundHeight/2.0f,//initial position(random.nextFloat()>0.5) ? 1f : -1f,//direction (random.nextFloat()>0.5) ? 1f : -1f,//direction 0.1f+random.nextFloat()*2.0f,//step size0.1f+random.nextFloat()*2.0f,//step size 0.5f+random.nextFloat()*0.5f,//scalenew Color(1.0f,1.0f,1.0f)));//color filter //This is an infected object. Set its life// expectancy. sprites.get(0).setLife((int)(random.nextFloat()*infectedSpriteLife)); //Populate the ArrayList object with green sprites.// Make the initial position random. Make the initial // direction of motion random. Make the speed// (step size) random. Make the size (scale) random. // Make the color filter white (do nothing).for(int cnt = 0;cnt<numberSprites;cnt++){ sprites.add(new Sprite01(greenBallImage,//image backgroundWidth*random.nextFloat(),//positionbackgroundHeight*random.nextFloat(),//position (random.nextFloat()>0.5) ? 1f : -1f,//direction (random.nextFloat()>0.5) ? 1f : -1f,//direction random.nextFloat()*maxStepSize,//step sizerandom.nextFloat()*maxStepSize,//step size 1.0f,//scalenew Color(1.0f,1.0f,1.0f)));//color filter }//end for loopgc.setTargetFrameRate(targetFPS);//set frame rate }//end init//----------------------------------------------------// @Overridepublic void update(GameContainer gc, int delta) throws SlickException{//Move all the sprites to their new positions. for(int cnt = 0;cnt<sprites.size();cnt++){ //Get a reference to the current Sprite01 object.Sprite01 thisSprite = sprites.get(cnt); //Ask the sprite to move according to its// properties thisSprite.move();//Ask the sprite to bounce off the edge if necessary thisSprite.edgeBounce(backgroundWidth,backgroundHeight); }//end for loop//Search for and process collisions between // infected (red) sprites and healthy (green)// sprites. Declare the green sprite to be exposed to // the disease when a collision occurs.for(int ctr = 0;ctr<sprites.size();ctr++){ //Get a reference to the Sprite01 object.Sprite01 testSprite = sprites.get(ctr); if(testSprite.getImage().equals(redBallImage)){//This is an infected sprite. Reduce its life. testSprite.setLife(testSprite.getLife() - 1);// Do the following for every sprite in the// ArrayList object. for(int cnt = 0;cnt<sprites.size();cnt++){ //Get a reference to the Sprite01 object.Sprite01 thisSprite = sprites.get(cnt);//Test for a collision between this sprite and // the infected test sprite.boolean collision = thisSprite.isCollision(testSprite);//Process a collision if it has occurred.// Exclude collisions between the testSprite // and itself and with other infected sprites.if((collision == true)&&(!thisSprite.getImage(). equals(redBallImage))){//A collision has occurred, set exposed to true thisSprite.setExposed(true);//Play a sound to indicate that a collision // has occurred.blaster.play(); }//end if}//end for loop}//end if on redBallImage//Make a cleanup pass through the ArrayList object Iterator<Sprite01>iterB = sprites.iterator();while(iterB.hasNext()){ Sprite01 theSprite = iterB.next();//Cause a percentage of the exposed objects to// contract the disease. Clear the others. if((theSprite.getExposed() == true)&&(random.nextFloat()<probabilityOfInfection)){ theSprite.setImage(redBallImage);theSprite.setLife((int)( random.nextFloat()*infectedSpriteLife));theSprite.setExposed(false); }else{//Eliminate the effects of the exposure theSprite.setExposed(false);}//end else//Remove dead sprites if(theSprite.getLife()<= 0){ iterB.remove();}//end if }//end while loop}//end outer for loop}//end update //----------------------------------------------------//public void render(GameContainer gc, Graphics g) throws SlickException{//set the drawing mode to honor transparent pixels g.setDrawMode(g.MODE_NORMAL);//Draw the background to erase the previous picture. background.draw(0,0);//Draw every sprite in the ArrayList object. for(int cnt = 0;cnt<sprites.size();cnt++){ sprites.get(cnt).draw();}//end for loop//Display the number of sprites remaining. g.drawString("Sprites remaining: " + (sprites.size()),100f,10f); }//end render}//end class Slick0220 //======================================================//

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In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
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Source:  OpenStax, Anatomy of a game engine. OpenStax CNX. Feb 07, 2013 Download for free at https://legacy.cnx.org/content/col11489/1.13
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