FallingSnow.java

import objectdraw.*;
import java.awt.*;

public class FallingSnow extends ActiveObject {
        
    // delay between snow motions
    private static final int DELAY_TIME = 33;  
    
    // lowest point in window
    private int screenHeight;             
    private DrawingCanvas canvas;
    
    // speed of fall
    private double ySpeed;        
    
    // the snowflake          
    private VisibleImage snow;           
    
    // initialize the instance variables and start the active object
    public FallingSnow(DrawingCanvas aCanvas, Image aSnowPic, 
                       double x, double aSpeed, 
                       int aScreenHeight) {
        canvas = aCanvas;
        ySpeed = aSpeed;
        screenHeight = aScreenHeight;
        
        snow = new VisibleImage(aSnowPic, 0, 0, canvas);
        snow.move(x, - snow.getHeight());
        
        start();
    }
    
    public void run() {
        
        // as long as tne snow is still on the screen
        // move it and pause
        while (snow.getY() < screenHeight ) {   
            pause(DELAY_TIME);
            snow.move(0,ySpeed);
        }  
        snow.removeFromCanvas();
    }
}

Snow.java

import objectdraw.*;
import java.awt.*;

// Program which creates clouds which create snow when the user clicks
public class Snow extends WindowController {
        
    // dimensions and location of the screen
    private static final int SCREEN_LEFT = 0;
    private static final int SCREEN_TOP = 0;
    private static final int SCREEN_HEIGHT = 400;
    private static final int SCREEN_WIDTH = 500;
    
    // constatnts for the moon size and location
    private static final int MOON_INSET = 50;
    private static final int MOON_SIZE = 70;
    
    // sizes and locations for the bricks
    private static final double BRICK_LINE = SCREEN_HEIGHT*0.85;
    private static final double BRICK_HEIGHT = SCREEN_HEIGHT*.04;
    private static final double SKYLINE = BRICK_LINE + BRICK_HEIGHT;
    private static final double BRICK_WIDTH = 30;
    private static final double BRICK_SPACING = 3;
    
    // colors of the sky, mortar, and brick
    private final Color NIGHTSKY = new Color(50, 50, 100);
    private final Color MORTAR = new Color(200, 200, 200);
    private final Color BRICKRED = new Color(150, 40, 40);
    
    // image of the snow
    private Image snowPic;
    
    public void begin() {
        
        // where to draw next brick
        double brickPosition;  
        
        // get leaf picture
        snowPic = getImage("snow.gif");
        
        // draw solid sky, mortar, and moon
        new FilledRect(0,0,SCREEN_WIDTH,SKYLINE,
                       canvas).setColor(NIGHTSKY);
        new FilledRect(0,SKYLINE,
                       SCREEN_WIDTH,SCREEN_HEIGHT-BRICK_LINE,
                       canvas).setColor(MORTAR);
        new FilledOval(MOON_INSET,MOON_INSET,MOON_SIZE,MOON_SIZE,
                       canvas).setColor(Color.white);
        
        // add the bricks
        brickPosition = 0;
        while ( brickPosition < SCREEN_WIDTH ) {
            new FilledRect(brickPosition, BRICK_LINE,
                           BRICK_WIDTH, BRICK_HEIGHT,
                           canvas).setColor(BRICKRED);
            
            brickPosition = brickPosition + BRICK_WIDTH + BRICK_SPACING;
        }
    }
        
    public void onMouseClick(Location point) {
        // make a new snow-dropping cloud when the user clicks
        new Cloud(snowPic, SCREEN_WIDTH, SCREEN_HEIGHT, canvas);
    }
}
        

Cloud.java

import objectdraw.*;
import java.awt.*;

public class Cloud extends ActiveObject {
    
    // total number of snowflakes
    private static final int MAX_SNOW = 150;   
    
    // the canvas
    private DrawingCanvas canvas;      
    
    // picture of a snowflake
    private Image snowPic;  
    
    // size of the screen
    private int screenWidth, screenHeight;
    
    // used to generate random speeds and positions for snowflakes
    private RandomIntGenerator snowGen;  
    
    public Cloud( Image aSnowPic,
                  int aScreenWidth, int aScreenHeight, 
                  DrawingCanvas aCanvas) {
        
        // save the parameters for the "run" method
        canvas = aCanvas;
        snowPic = aSnowPic;
        screenWidth = aScreenWidth;
        screenHeight = aScreenHeight;
        
        snowGen = new RandomIntGenerator( 0, screenWidth);
        
        start();
    }
    
    public void run()
    {
        int snowCount = 0;
        
        // continue creating snow until the maximum amount
        // has been created
        while (snowCount < MAX_SNOW ) {
            
            snowCount = snowCount + 1;
            
            new FallingSnow(canvas, snowPic, 
                            snowGen.nextValue(),   // x coordinate
                            snowGen.nextValue()*2/screenWidth+2, // y speed
                            screenHeight);
            pause(900);
        }
    }
}