public class WaterSpout {

    static double ySpread = 0.2;  // Vertical distance between droplets.
    static double xSpread = 0.3;  // Max horizontal movement.

    public static void main (String[] argv)
    {
	DrawTool.display ();
	DrawTool.setXYRange (0,10, 0,10);


	// Number of droplets.
	int n = 100;

	DrawTool.startAnimationMode ();

	// Initially, all will start in the middle at height 10.
	double[] x = makeXCoords (n, 5);
	double[] y = makeYCoords (n, 10);

	// As long as the last drop is above ground, simulate.
	while (y[n-1] > 0) {
	    movePoints (x, y);
	    drawPoints (x, y);
	    DrawTool.animationPause (100);
	}
	DrawTool.endAnimationMode ();

	// Draw final landing points in blue.
	y = new double [n];
	DrawTool.setPointColor ("blue");
	drawPoints (x,y);
    }


    static double[] makeXCoords (int n, double initValue)
    {
	double[] x = new double [n];
	for (int i=0; i<n; i++) {
	    x[i] = initValue;
	}
	return x;
    }


    static double[] makeYCoords (int n, double initValue)
    {
	double[] y = new double [n];
	y[0] = initValue;
	for (int i=1; i<n; i++) {
	    // Change the height so that the drops
	    // come one by one.
	    y[i] = y[i-1] + ySpread;
	}
	return y;
    }


    static void movePoints (double[] x, double[] y)
    {
	for (int i=0; i<x.length; i++) {
	    y[i] = y[i] - ySpread;
	    if (y[i] <= 10) {
		double r = Math.random ();
		if (r < 0.33) {
		    x[i] = x[i] - xSpread * Math.random();
		}
		else if (r < 0.66) {
		    x[i] = x[i] + xSpread * Math.random();
		}
	    }
	}
    }

    static void drawPoints (double[] x, double[] y)
    {
	for (int i=0; i<x.length; i++) {
	    if (( y[i] >= 0) && (y[i] <= 10));
	    DrawTool.drawPoint (x[i], y[i]);
	}
    }

}