Universe.java in pgm

Universe.java

public class Universe

{

    private final double radius;    

    private final int N;            

    private final Body[] orbs;      

                public Universe()

   {

        N = StdIn.readInt();

        radius = StdIn.readDouble();

        StdDraw.setXscale(-radius, +radius);

        StdDraw.setYscale(-radius, +radius);

        orbs = new Body[N];

        for (int i = 0; i < N; i++)

{

            double rx   = StdIn.readDouble();

            double ry   = StdIn.readDouble();

            double vx   = StdIn.readDouble();

            double vy   = StdIn.readDouble();

            double mass = StdIn.readDouble();

            double[] position = { rx, ry };

            double[] velocity = { vx, vy };

            Vector r = new Vector(position);

            Vector v = new Vector(velocity);

            orbs[i] = new Body(r, v, mass);

        }

    }

               public void increaseTime(double dt)

               {

                    Vector[] f = new Vector[N];

        for (int i = 0; i < N; i++)

        {

        f[i] = new Vector(new double[2]);

        }

        for (int i = 0; i < N; i++)

            {

            for (int j = 0; j < N; j++)

            {

                if (i != j)

            {

                    f[i] = f[i].plus(orbs[i].forceFrom(orbs[j]));

                }

            }

        }

        for (int i = 0; i < N; i++)

       {

            orbs[i].move(f[i], dt);

        }

    }

             public void draw()

            {

        for (int i = 0; i < N; i++)

        {

            orbs[i].draw();

        }

    }

                public static void main(String[] args)

                {

        Universe newton = new Universe();

        double dt = Double.parseDouble(args[0]);

        while (true)

     {

            StdDraw.clear();

            newton.increaseTime(dt);

            newton.draw();

            StdDraw.show(10);

        }

    }

}