import java.awt.*;
import java.lang.String;
import java.applet.Applet;
import java.net.URL;
import java.lang.Integer;

/** A class for holding a sequence of Images.  Used by AnimatedSprite for a series of images
shown one after the other.  Used by PointSprite to hold the various rotations of an image, starting
with due right.
*/
public class Sequence extends Object {
	Image frame[];
	MediaTracker tracker;
	int width, height;  // not currently used
	
/** Loads images and builds Sequence object.  Uses MediaTracker to force complete image loading.
Uses Applet.showStatus() to inform user of progress in loading images.
@param name A stub for the images' filenames, in the current document base.  Images start at 0
and are given a ".gif" suffix.  So, name "graphics/ball" looks in a "graphics" folder in the current
document base for files named "ball0.gif", "ball1.gif", etc.
@param num Number of images to load into the sequence
@param applet Calling applet.  Needed to inform user of image-loading progress
*/
	public Sequence (String name, int num, Applet applet) {
		int counter;
		URL documentBase = applet.getDocumentBase();
 		tracker = new MediaTracker(applet);
		frame = new Image [num];
		
		for (counter = 0; counter < num; counter++) {
			frame[counter] = applet.getImage (documentBase,
				name + Integer.toString (counter) + ".gif");
			tracker.addImage (frame[counter], 0);	
		} /* for */
		
		applet.showStatus ("Getting sprite images: " + name);
		try  {
			tracker.waitForID(0);
		} catch (InterruptedException e) { } 

	} /* full constructor */


/** Returns the image at the specified index of this Sequence.
@param index The index of the image to return
@return The image at the specified index.  If index is negative or greater than the length of the
sequence, returns null.
*/
	public Image imageAt (int index) {
		if ((index >=0) | (index <= frame.length)) {
			return frame[index];
		} else {
			return null;
		}
		
	} // imageAt
	
/** Returns length of the Sequence, ie, how many images are in it
@return Length of the Sequence
*/
	public int getLength () {
		return frame.length;	
	}
	
}