Computer Science 252
Problem Solving with Java

Spring 2016, The College of Saint Rose

Lab 6: Flowers
Due: 11:59 PM, Tuesday, February 23, 2016

In this lab, you will gain experience working with a custom object by writing a program that grows and displays some flowers, much like those that bloom throughout the Albany area this time of year (or not).

When you press the mouse on the canvas, a small plant is drawn. As you drag the mouse, the plant grows slowly. When it reaches its full height, a flower blooms. If you then click on that flower's petals before beginning to work on the next flower, its color will change.

You may work alone or with a partner on this lab.

Getting Set Up

To help you get started, we have provided a starter BlueJ project with the class header and some method stubs for the Flower class and a complete version of a WindowController extension named Spring that will manipulate the flowers on the screen using the constructor and methods of the Flower class. You will need to create your own class GrowingRectangle for the practice program.

Working solutions to all programs can be downloaded here.

Practice Program

Before we get in to the programming assignment, there is a practice program for you to complete. Please do this first, as it will help you with some of the essential functionality of the programming assignment.

The program should have this functionality:

  1. A black rectangle is created when the program starts.
  2. When the mouse moves on top of the rectangle, the rectangle grows vertically, with its base remaining fixed. However, it should never grow larger than 200 in height. When it reaches 200 in height, it should be colored red.
  3. When the mouse is dragged on top of the rectangle, the rectangle shrinks vertically, again with its base remaining fixed. However, it should never shink to less than 50 in height. When it reaches 50 in height, it should be colored blue.
  4. Any time the height of the rectangle is greater than 50 but less than 200, it should be black again.

Programming Assignment: Spring Flowers

Design Document

To get started, you will develop a written design for this program, no later than our class meeting on Thursday, February 18. Before you write anything down, read this entire lab description carefully. Then develop a design that includes:

Do not start coding before completing this design and having it approved by your instructor. It is often more productive to design a program away from the computer, and you should get into the habit of working in this way. If you arrive at the keyboard with a written idea of how to approach the problem, you will be able to make progress much more quickly than you would otherwise.

Problem Description

The canvas should initially start empty. When you click on the canvas, a flower should start growing with its base centered at that point. Initially it will be just a sprout, the height of which you may choose to be either a constant value or a percentage of the ultimate height of the flower. Its final height is determined by the second formal parameter to the constructor. As you drag the mouse, the stem should grow (upward, obviously). When it reaches its full height, the stem should stop growing and petals should appear. The color for the petals should be chosen randomly. The flower should not grow any more, but if you click on the petals after it has bloomed, the flower will change color. When you are happy with the flower's color, you can grow another one by clicking somewhere else in the window. When the mouse moves out of and then back into the window, the flowers should be removed from the canvas. Only the most-recently-created flower needs to respond to mouse clicks by changing its color.

If the mouse is released before the stem reaches its full height, the stem's growth stops and this plant will never produce a flower.

Your program will be divided into two classes: a window controller called Spring and a Flower class. A complete Spring class, which you should not modify, is provided in the starter folder. Your task is to implement the Flower class so that it works with our Spring. In particular, the Flower class needs to provide:

  1. A constructor that takes three parameters: the Location where the Flower's stem should be planted, a double specifying the maximum height of the Flower, and the canvas.
  2. A mutator method public void changeColor(): sets the color of the flower petals to a random color. This may be completely random, or you may restrict to colors that you think look nice.
  3. An accessor method public boolean flowerContains(Location point): returns true if the petals or center of the flower contains the point.
  4. A mutator method public void grow(): make the flower grow a bit if it has not already reached its full size and sprouted petals. Growing by about 1 for each mouse drag event is an appropriate rate of growth.

Your flowers should be at least as realistic as those in the demo solution. But feel free to use more graphics primitives in your Flower class to make the flowers look more attractive. Up to 3 bonus points are available for especially nice flowers.

Important note: your program should not include any loops! The growth of the flowers is controlled by the sequence of mouse drag events.


Before 11:59 PM, Tuesday, February 23, 2016, submit your lab for grading. There are three things you need to do to complete the submission: (i) Email a copy of your lab (a .7z or .zip file containing your project directory) to terescoj AT (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).


This assignment is worth 60 points, which are distributed as follows:

> FeatureValueScore
GrowingRectangle correctness 10
Spring Flowers Initial Design
Sufficient detail to convey the basic design of Flower 4
Includes picture of flower layout with dimensions 2
Spring Flowers Style, Design, and Efficiency
Appropriate comments 3
Good variable names 2
Appropriate variable declarations 3
Good use of constants 4
Appropriate formatting 1
Does not generate new objects unnecessarily 2
Good overall design and methods 3
Spring Flowers Correctness
Initial stem drawn properly 4
Stem grows while mouse is dragged 7
Growth stops at specified height 4
Flower appears when height is achieved 7
Color changes when most recent petals clicked 4
Spring Flowers Extra Credit
Nicer flowers 3
Total 60