Need to import ArrayList

Description of a park:

(1) a park has:

  - a bunch of balloons (ArrayList)
  - a bunch of flowers  (ArrayList)

(2) a park can be created:


  - by specifying nothing, but
    creating empty storage
    for the balloons and flowers


(3) a park can do:


  - receive a single balloon and 
    add it to its set of balloons




  - ask all balloons to move a bit

    estimate wind speed

    get i-th balloon

    ask i-th balloon to
    move and draw itself

package cs1.ParkApp;

import cs1.app.*;
import java.util.ArrayList;

public class Park
{
    // the features (data members)
    
    private ArrayList<Balloon> balloonsList;
    // private ArrayList<Flower> flowersList;
    
    // the constructor(s)
    
    public Park()
    {
        balloonsList = new ArrayList<Balloon>();     // make empty set of balloons
        // flowersList = new ArrayList<Flower>();       // make empty set of flowers
    }
    
    // the behaviors (methods)
    
    public void add( Balloon balloon )
    {
        balloonsList.add( balloon );
    }

    public void driftBalloons( )
    {
        for ( int i = 0 ; i < balloonsList.size() ; i++ )
        {
            double dx = canvas.getRandomDouble( -3, 3 );
            double dy = -1;
                
            Balloon balloon = balloonsList.get( i );
            
            balloon.drift( dx, dy );
            balloon.draw();
        }
    }
}