GravSim Source Code
File gravsim.java:
/*
Trivial applet that displays two object that move perpendicular to each other.
*/
import java.awt.*;
import java.applet.*;
import java.math.*;
public class gravsim extends Applet implements Runnable
{ //Initianlise member variables
Thread mThread; //new Thread
Image mBuffer; // image Buffer
Rectangle mBackground; //Reactagles
Rectangle mBodyRect1;
Rectangle mBodyRect2;
// Image mbody1; //Images
// Image mbody2;
Button mStart, mStop, mReset; //Buttons
Checkbox mTrace = new Checkbox("Trace");
boolean bIsDrawing = false; //Booleans
boolean bOver = true;
boolean bTrace = false;
int mRep;
double mRatio = 10e8;
double mXpos1 = 0, mYpos1 = 0;
double mXpos2 = 0;
double mYpos2 = 0;
double mXacc1 = 0, mXacc2 = 0;
double mYacc1 = 0, mYacc2 = 0;
double mbody2mass = 6e24, mbody1mass = 2e30;
double mTime = 3.6e-4;
int mSleepValue = 10; //Sleep value
double mDistancex;
double mDistancey;
double mDistanceF;
public void init()
{ //init the process and construct variables
Dimension d = size();
mBuffer = createImage(d.width, d.height);
// mbody1 = getImage(getDocumentBase(), "star.gif");
// mbody2 = getImage(getDocumentBase(), "star.gif");
mStart = new Button("start");
mStop = new Button("pause");
mReset = new Button("reset");
mReset.disable();
mStop.disable();
MediaTracker mt = new MediaTracker(this); // Create Media Tracker..
// mt.addImage(mbody2,0); // Add the images
// mt.addImage(mbody1,0);
add(mStart);
add(mStop);
add(mReset);
add(mTrace);
mRep = 1;
mDistanceF = 1;
mDistancex = 1;
mDistancey = 1;
mBodyRect1 = new Rectangle(d.width/2,d.height/2,2,2);
mBodyRect2 = new Rectangle((d.width/2),(d.height/2+150),1,1);
try
{
mt.waitForID(0);
}
catch(Exception e)
{
e.printStackTrace();
}
repaint();
}
public void movebodies() //Function to actually move the bodys
{
Dimension d = size();
mYpos1 += mYacc1;
mXpos1 += mXacc1;
mXpos2 += mXacc2;
mYpos2 += mYacc2;
mBodyRect1.move((int)((mXpos1/mRatio)+(d.width/2)),(int)((mYpos1/mRatio)+d.height/2));
mBodyRect2.move((int)((mXpos2/mRatio)+(d.width/2)),(int)((mYpos2/mRatio)+d.height/2));
}
public void distance() // Get the distance points
{
mDistancex = ((mXpos1)-(mXpos2));
mDistancey = ((mYpos1)-(mYpos2));
mDistanceF = Math.sqrt((Math.pow(mDistancex,2.0))+(Math.pow(mDistancey,2.0)));
}
public void gravity1() //New class called Gravity
{
double mgravconst = 6.67e-11;
mYacc1 +=((mDistancey)*(mbody2mass))*mgravconst*mTime/(Math.pow(mDistanceF,2.0));
mXacc1 +=((mDistancex)*(mbody2mass))*mgravconst*mTime/(Math.pow(mDistanceF,2.0));
}
public void gravity2() //New class called Gravity
{
double mgravconst = 6.67e-11;
mXacc2 += ((mDistancex)*(mbody1mass))*mgravconst*mTime/(Math.pow(mDistanceF,2.0));
mYacc2 += ((mDistancey)*(mbody1mass))*mgravconst*mTime/(Math.pow(mDistanceF,2.0));
}
public boolean action(Event evt, Object what) //Event trapping
{
if(evt.target == mStart)
{
if(bOver)
{
resetOrbit();
}
startOrbit();
}
if(evt.target == mStop)
{
pause();
}
if(evt.target == mReset)
{
resetOrbit();
repaint();
}
if(evt.target == mTrace)
{
if(!mTrace.getState())
{
mTrace.setState(false);
bTrace = false;
}
else{
mTrace.setState(true);
bTrace = true;
}
}
return false;
}
public void pause() //if stop is pushed
{
mStart.enable();
mReset.enable();
mThread.stop();
mStart.enable();
mStop.disable();
}
public void startOrbit() //Start the applet when Start is pushed
{
mStart.disable();
mReset.disable();
mStop.enable();
bOver = false;
mThread = new Thread(this);
mThread.setPriority(Thread.MIN_PRIORITY);
mThread.start();
}
public void resetOrbit() // called when button or interception occurs
{
Dimension d = size();
mYacc1 = 0;
mXacc1 = 0;
mYacc2 = 0;
mXacc2 = 0.2e9;
mXpos1 = 0;
mBodyRect1.x = /*(int)(mXpos1/mRatio)+*/ (d.width/2);
mYpos1 = 0;
mBodyRect1.y = /*(int)(mYpos1/mRatio)+*/ (d.height/2);
mXpos2 = 0;
mBodyRect2.x = (d.width/2)+ (int)(mXpos2/mRatio);
mYpos2 = 1.5e11;
mBodyRect2.y = (d.height/2)+ (int)(mYpos2/mRatio);
mRep = 1;
distance();
repaint();
}
public void stop()
{
bOver = true;
mStart.enable();
if(mThread != null)
{
mThread.stop();
}
}
public void update(Graphics g)
{
paint(g);
}
public void paint( Graphics g )
{
Graphics bg = mBuffer.getGraphics();
Dimension d = size();
// bg.clearRect(0,0,d.width,d.height);
bg.setColor(Color.black);
// bg.drawRect(0, 0,d.width,d.height);
if(!bTrace || mRep < 2)
{
bg.setColor(Color.black);
bg.fillRect(0, 0,d.width,d.height);
}
bg.setColor(Color.red);
bg.drawRect(mBodyRect1.x,mBodyRect1.y,mBodyRect1.width,mBodyRect1.height);
bg.setColor(Color.blue);
bg.drawRect(mBodyRect2.x,mBodyRect2.y,mBodyRect2.width,mBodyRect2.height);
// bg.drawImage(mbody1,mbodyRect1.x,mbodyRect1.y,this);
// bg.drawImage(mbody2,mbodyRect2.y,mbodyRect2.x,this);
bg.setColor(Color.black);
bg.fillRect(30,30,140,100);
bg.setColor(Color.green);
bg.drawRect(29,19,143,72);
bg.setColor(Color.white);
bg.drawString("Rep-"+mRep, 30, 90 );
bg.drawString("GravSim 1.0", 30, 30 );
bg.drawString("Sleep- "+mSleepValue, 30,40);
// bg.drawString("Distance-"+mDistancex+","+mDistancey+","+mDistanceF,30,50);
// bg.drawString("Pos1-"+mXpos1+","+mYpos1,30,60);
// bg.drawString("Pos2-"+mXpos2+","+mYpos2,30,70);
bg.drawString("Location-"+mBodyRect1.x+","+mBodyRect1.y+"."+mBodyRect2.x+","+mBodyRect2.y,30,50);
bg.drawString("Mass1-"+mbody1mass,30,60);
bg.drawString("Mass2-"+mbody2mass,30,70);
bg.drawString("Raw Distance-"+((mBodyRect2.x)-(mBodyRect1.x))+","+((mBodyRect2.y)-(mBodyRect1.y)),30,80);
// bg.drawString("Velocity-"+mXacc1+","+mYacc1+"."+mXacc2+","+mYacc2,30,120);
g.drawImage(mBuffer,0,0,null);
bIsDrawing = false;
}
public void run()
{
Dimension d = size();
while (true)
{
distance();
gravity1();
gravity2();
movebodies();
mRep++;
try
{
if(mSleepValue != 0)
{
mThread.sleep(mSleepValue); //slow the whole thing down
}
}
catch(Exception e)
{
System.out.println(e);
}
if(!bIsDrawing)
{
bIsDrawing = true;
repaint();
}
}
}
}
Author: Luke Andrews-Hakken
Homepage: http://newmedia.slc.edu/~luke/astro
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