Untitled

package checkPoint;

import java.util.ArrayList;//imports arraylist class
import edu.princeton.cs.introcs.StdDraw;

public class System {//helped by Andre Soto and TA Julia
    public double G = 6.67384e-11;//Universal Gravitational Constant
    //creates an array list for our objects to be put into
    ArrayList<Body> BODYLIST;
    //initializes array
    public void system(ArrayList<Body> bodyList) {//calculates acceleration for each body
        BODYLIST = bodyList;
    }
    public double[] computeAcceleration(Body planet) {
        double ax = 0;//x acceleration
        double ay = 0;//y acceleration
        double changeY = 0;//change in y
        double changeX = 0;//change in x
        double a; //acceleration
        double r = 0; //radius

        for (int i = 0; i < BODYLIST.size(); i++) {//for loop to give us an arraylist making our bodies in the system
            if (planet.equals(BODYLIST.get(i))) {
                continue;
            }
            changeX = BODYLIST.get(i).X - planet.X;//changes x
            changeY = BODYLIST.get(i).Y - planet.Y;//changes y
            r = Math.sqrt(changeX*changeX + changeY*changeY);//makes the radius
            a = G * BODYLIST.get(i).MASS / (r*r);//makes the acceleration
            ax += a * changeX / r;
            ay += a * changeY / r;
        }
        double[] acceleration = new double[2];//uses an array to make the acceleration
        acceleration[0] = ax;//x acceleration
        acceleration[1] = ay;//y acceleration


        return acceleration;//gives us acceleration
    }
    public void update(double timestep) {//updates things
        double[] as;
        for (int i = 0; i < BODYLIST.size(); i++) {
            as = computeAcceleration(BODYLIST.get(i)); //updates acceleration
            BODYLIST.get(i).updateVelocity(as[0], as[1], timestep);//updates velocity
            BODYLIST.get(i).updatePosition(timestep);//updates position
        }
    }

    public void draw(double cx, double cy, double pixelsPerMeter) {//drawsthe body
        StdDraw.clear(StdDraw.BLACK);
        for (int i = 0; i < BODYLIST.size(); i++) {
            BODYLIST.get(i).draw(cx, cy);
        }
        StdDraw.show(20);//updates every 20 milliseconds
    }

}