Computer Science 252
Problem Solving with Java

Spring 2014, The College of Saint Rose

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Spring is around the corner, the birds are coming back. So we'll develop some programs with an avian theme.

You may work alone or with a partner on this lab. Only one submission per group is needed.

There are two practice programs and two programming assignments in this lab. Please refer to the "Submission Guidelines" on the course home page and syllabus for the requirements for each of these items.

Getting Set Up

Working solutions to all programs can be downloaded here.

Download the a starter project with partial implementations of some of the programs from here.

Practice

First, you'll practice a technique similar to one you'll need in the first programming assignment: making an object grow taller.

A few notes on this one:

• You don't need a loop! The rectangle should grow a bit each time the mouse moves inside its bounds. Once it reaches its full height and turns red, all mouse move events should be ignored.
• Don't create the rectangle more than once. Just move, resize, and change the color of the one you start out with.

Irate Ibises

Your first of two programming assignments is to complete a program that draws some birds (we'll think of them as ibises, since they're going to be tall birds, hence the name "irate ibises", which I hear is the next hit app from Rovio).

The canvas initially starts empty. When you press the mouse on the canvas, an ibis starts growing at that point. Initially it will be just a short bird with a body, beak, and legs. The bird's body may be of a color of your choosing. The base of the bird's body should be at the press point. As you drag the mouse around, it grows taller. When it reaches its full height, the bird stops growing and eyes appear. The ibis won't grow any more, but if you press on its eyes after the bird has reached full size, its body should change to a new randomly generated color. When you are happy with the ibis's color, you can grow another one by pressing somewhere else in the window.

Your program should be divided into two classes: a window controller called IrateIbises and an Ibis class. The starter folder provides a complete IrateIbises class, which you should not modify. Your task is to complete the partially-implemented Ibis class so that it works with the provided IrateIbises. In particular, the Ibis constructor takes two parameters: the Location of the bottom of the bird's body and the canvas, and draws the initial ibis. You are welcome to use this code or replace it with one of your own design. The Ibis class defines "stubs" for the following methods which are used by the controller to implement the functionality described above:

• public void changeColor(): sets the color of the ibis body to a random color.
• public boolean eyesContain(Location point): returns true if either of the eyes contains the point.
• public void grow(): make the ibis grow a bit, or make the eyes appear when it reaches its full height. The ibis will only grow when the mouse is dragged, so Ibis should not extend ActiveObject.

Demo

A working solution for the program will appear below. Click inside the applet to interact with it.

More Practice

Since your second programming project involves an ActiveObject a bit different from the ones you've seen, we'll start with a practice program to create an ActiveObject that behaves similarly.

In the BallTossAround folder in the starter you downloaded, you will find a window controller class called BallTossAround that creates a FilledOval every time you press the mouse and passes that FilledOval to the constructor of an active object (which you will implement) that is responsible for moving that ball across the screen as if you "tossed" it upward to the right.

Most (all?) of the active objects we have seen so far are responsible for creating the graphical objects they animate. Here, though, the active object takes the object it animates as a parameter to the constructor.

Specifically, the active object's constructor should remember the ball it is passed, remember the canvas (or perhaps just its dimensions) so when the run method animates the ball, it can stop when the ball goes off the bottom or right of the canvas. Its run method should start the ball moving up and to the right, but the ball should be subject to "gravity" - its y speed should increase each time around the animation loop. So you should see the ball trace out a parabolic path. When the ball goes off the bounds of the canvas, the loop should stop and the ball should be removed from the canvas.

Angry Bird

Your final task is to implement a very simplified version of the popular Angry Birds game, where millions of people spend billions of combined hours launching birds at pigs. (Note that I am not judging or criticizing here, I am a recovering Angry Birds addict.) Since your program will have just one bird and one pig, maybe we'd call it "Angry Bird".

The program stars with a bird sitting on a perch near the bottom left and a pig sitting somewhere near the bottom right of the canvas. To play, you press the mouse and drag around near the bird, resulting in a "sling" that follows your mouse around on one end but which remains anchored to the bird on the other. When you release the mouse, the angle of the sling determines a "launch vector" for the bird. The bird starts moving in the direction you launched him, and flies across the canvas, subject to acceleration due to gravity. The game ends in success if your bird bumps into the pig, or failure if your bird leaves the visible bounds of the canvas before bumping into the pig.

A few more details, hints, and other notes:

• Since your bird is already on the canvas before it starts to be animated, you will use the same idea as in the practice program, where you pass the graphical object to be animated as a parameter to the constructor of the active object.
• The pig should be placed somewhere in the lower right 75 ×75 corner of the canvas.
• There should be a message displayed near the top of the canvas that gives game instructions that change as appropriate depending on whether the mouse has not yet been pressed, the player is dragging to select a launch vector, the bird is in transit, or the game has been won or lost. Note that since the win/lose decision can only be made when the bird hits the pig or leaves the canvas, your active object that controls the bird's flight will need to know about the Text object that contains the message.
• There are a number of image files provided that you can use to create VisibleImage objects of the bird and pig. Note that this is only a small part of this assignment and you can earn nearly full credit if you use a couple of FilledOvals to represent the bird and pig.
• You will probably want a larger canvas than the default 400 ×400 for this program. Note that your program should work for any (reasonable) size canvas.

Demo

A working solution for the program will appear below. Click inside the applet to interact with it.

Bonus Opportunity

You can earn up to 10 points of bonus for enhancements to the two programming assignments. Check with your instructor for details.

Submitting

Before 4:00 PM, Friday, February 28, 2014, submit your lab for grading. There are four things you need to do to complete the submission: (i) Upload a copy of your lab (a .7z or .zip file containing your project directory) using Submission Box under assignment "Lab4". (ii) Demonstrate the execution of your programs for your instructor. (iii) Hand a printout of the Java files that make up the programming assignment (not practice programs) to your instructor. (2 business day grace period for demos and printouts).

Grading

This assignment is worth 100 points, which are distributed as follows: