了解下JAVA的庞大性实际 - 仓酷云

//:FieldOBeasts.java
//Demonstrationofcomplexitytheory;simulates
//herdingbehaviorinanimals.Adaptedfrom
//aprogrambyLarryOBrienlobrien@msn.com
importjava.awt.*;
importjava.awt.event.*;
importjava.applet.*;
importjava.util.*;
classBeast{
int
x,y,//Screenposition
currentSpeed;//Pixelspersecond
floatcurrentDirection;//Radians
Colorcolor;//Fillcolor
FieldOBeastsfield;//WheretheBeastroams
staticfinalintGSIZE=10;//Graphicsize
publicBeast(FieldOBeastsf,intx,inty,
floatcD,intcS,Colorc){
field=f;
this.x=x;
this.y=y;
currentDirection=cD;
currentSpeed=cS;
color=c;
}
publicvoidstep(){
//Youmovebasedonthosewithinyoursight:
Vectorseen=field.beastListInSector(this);
//Ifyourenotoutinfront
if(seen.size()>0){
//Gatherdataonthoseyousee
inttotalSpeed=0;
floattotalBearing=0.0f;
floatdistanceToNearest=100000.0f;
BeastnearestBeast=
(Beast)seen.elementAt(0);
Enumeratione=seen.elements();
while(e.hasMoreElements()){
BeastaBeast=(Beast)e.nextElement();
totalSpeed+=aBeast.currentSpeed;
floatbearing=
aBeast.bearingFromPointAlongAxis(
x,y,currentDirection);
totalBearing+=bearing;
floatdistanceToBeast=
aBeast.distanceFromPoint(x,y);
if(distanceToBeast<distanceToNearest){
nearestBeast=aBeast;
distanceToNearest=distanceToBeast;
}
}
//Rule1:Matchaveragespeedofthose
//inthelist:
currentSpeed=totalSpeed/seen.size();
//Rule2:Movetowardstheperceived
//centerofgravityoftheherd:
currentDirection=
totalBearing/seen.size();
//Rule3:Maintainaminimumdistance
//fromthosearoundyou:
if(distanceToNearest<=
field.minimumDistance){
currentDirection=
nearestBeast.currentDirection;
currentSpeed=nearestBeast.currentSpeed;
if(currentSpeed>field.maxSpeed){
currentSpeed=field.maxSpeed;
}
}
}
else{//Youareinfront,soslowdown
currentSpeed=
(int)(currentSpeed*field.decayRate);
}
//Makethebeastmove:
x+=(int)(Math.cos(currentDirection)
*currentSpeed);
y+=(int)(Math.sin(currentDirection)
*currentSpeed);
x%=field.xExtent;
y%=field.yExtent;
if(x<0)
x+=field.xExtent;
if(y<0)
y+=field.yExtent;
}
publicfloatbearingFromPointAlongAxis(
intoriginX,intoriginY,floataxis){
//ReturnsbearingangleofthecurrentBeast
//intheworldcoordiantesystem
try{
doublebearingInRadians=
Math.atan(
(this.y-originY)/
(this.x-originX));
//Inversetanhastwosolutions,soyou
//havetocorrectforotherquarters:
if(x<originX){
if(y<originY){
bearingInRadians+=-(float)Math.PI;
}
else{
bearingInRadians=
(float)Math.PI-bearingInRadians;
}
}
//Justsubtracttheaxis(inradians):
return(float)(axis-bearingInRadians);
}catch(ArithmeticExceptionaE){
//Divideby0errorpossibleonthis
if(x>originX){
return0;
}
else
return(float)Math.PI;
}
}
publicfloatdistanceFromPoint(intx1,inty1){
return(float)Math.sqrt(
Math.pow(x1-x,2)+
Math.pow(y1-y,2));
}
publicPointposition(){
returnnewPoint(x,y);
}
//Beastsknowhowtodrawthemselves:
publicvoiddraw(Graphicsg){
g.setColor(color);
intdirectionInDegrees=(int)(
(currentDirection*360)/(2*Math.PI));
intstartAngle=directionInDegrees-
FieldOBeasts.halfFieldOfView;
intendAngle=90;
g.fillArc(x,y,GSIZE,GSIZE,
startAngle,endAngle);
}
}
publicclassFieldOBeastsextendsApplet
implementsRunnable{
privateVectorbeasts;
staticfloat
fieldOfView=
(float)(Math.PI/4),//Inradians
//Deceleration%persecond:
decayRate=1.0f,
minimumDistance=10f;//Inpixels
staticint
halfFieldOfView=(int)(
(fieldOfView*360)/(2*Math.PI)),
xExtent=0,
yExtent=0,
numBeasts=50,
maxSpeed=20;//Pixels/second
booleanuniqueColors=true;
ThreadthisThread;
intdelay=25;
publicvoidinit(){
if(xExtent==0&&yExtent==0){
xExtent=Integer.parseInt(
getParameter("xExtent"));
yExtent=Integer.parseInt(
getParameter("yExtent"));
}
beasts=
makeBeastVector(numBeasts,uniqueColors);
//Nowstartthebeastsa-rovin:
thisThread=newThread(this);
thisThread.start();
}
publicvoidrun(){
while(true){
for(inti=0;i<beasts.size();i++){
Beastb=(Beast)beasts.elementAt(i);
b.step();
}
try{
thisThread.sleep(delay);
}catch(InterruptedExceptionex){}
repaint();//Otherwiseitwontupdate
}
}
VectormakeBeastVector(
intquantity,booleanuniqueColors){
VectornewBeasts=newVector();
Randomgenerator=newRandom();
//UsedonlyifuniqueColorsison:
doublecubeRootOfBeastNumber=
Math.pow((double)numBeasts,1.0/3.0);
floatcolorCubeStepSize=
(float)(1.0/cubeRootOfBeastNumber);
floatr=0.0f;
floatg=0.0f;
floatb=0.0f;
for(inti=0;i<quantity;i++){
intx=
(int)(generator.nextFloat()*xExtent);
if(x>xExtent-Beast.GSIZE)
x-=Beast.GSIZE;
inty=
(int)(generator.nextFloat()*yExtent);
if(y>yExtent-Beast.GSIZE)
y-=Beast.GSIZE;
floatdirection=(float)(
generator.nextFloat()*2*Math.PI);
intspeed=(int)(
generator.nextFloat()*(float)maxSpeed);
if(uniqueColors){
r+=colorCubeStepSize;
if(r>1.0){
r-=1.0f;
g+=colorCubeStepSize;
if(g>1.0){
g-=1.0f;
b+=colorCubeStepSize;
if(b>1.0)
b-=1.0f;
}
}
}
newBeasts.addElement(
newBeast(this,x,y,direction,speed,
newColor(r,g,b)));
}
returnnewBeasts;
}
publicVectorbeastListInSector(Beastviewer){
Vectoroutput=newVector();
Enumeratione=beasts.elements();
BeastaBeast=(Beast)beasts.elementAt(0);
intcounter=0;
while(e.hasMoreElements()){
aBeast=(Beast)e.nextElement();
if(aBeast!=viewer){
Pointp=aBeast.position();
Pointv=viewer.position();
floatbearing=
aBeast.bearingFromPointAlongAxis(
v.x,v.y,viewer.currentDirection);
if(Math.abs(bearing)<fieldOfView/2)
output.addElement(aBeast);
}
}
returnoutput;
}
publicvoidpaint(Graphicsg){
Enumeratione=beasts.elements();
while(e.hasMoreElements()){
((Beast)e.nextElement()).draw(g);
}
}
publicstaticvoidmain(String[]args){
FieldOBeastsfield=newFieldOBeasts();
field.xExtent=640;
field.yExtent=480;
Frameframe=newFrame("FieldOBeasts");
//Optionallyuseacommand-lineargument
//forthesleeptime:
if(args.length>=1)
field.delay=Integer.parseInt(args[0]);
frame.addWindowListener(
newWindowAdapter(){
publicvoidwindowClosing(WindowEvente){
System.exit(0);
}
});
frame.add(field,BorderLayout.CENTER);
frame.setSize(640,480);
field.init();
field.start();
frame.setVisible(true);
}
}///:~
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