This is an assignment to the Software Architecture class at the Technische Hochschule Nürnberg.

Assignment 5: Generics and Bounds

This assignment covers an advanced topic of generics: bounds on type parameters and wildcards. Bounds describe type constraints of generic classes or methods that allow to balance type safety with flexibility of use.

Setup

1. Create a fork of this repository (button in the right upper corner)
2. Clone the project (get the link by clicking the green Clone or download button)
3. Import the project to your IDE (remember the guide in assignment 1)
4. Validate your environment by running the tests from your IntelliJ and by running gradle test on the command line.

Groundwork

First, create the model for this assigment:

1. Create the enum PlantColor
2. Implement the abstract class Plant
3. Implement the child classes Flower and Shrub
   Remarks:
   • A shrub is always green; a flower may be any color but green (handle a wrong value in the constructor)
   • Flowers compare to each other by height
   • All good data classes should always implement equals and hashCode, ideally also toString.
4. Create tests to ensure that your model classes are correct (e.g. green flowers won't work)

Basic Bounds

Implement a PlantBed which manages a list of plants (use SimpleList<T>).

A PlantBed may contain any subclass of Plant but nothing else! Use appropriate bounds when declaring the generic class.

Remarks: The method getPlantsByColor is very easy to implement if you think of the filter method of the SimpleList! Remember to create tests for nearly every line you code!

Bounds on Wildcards

Last but not least we'll look at the PECS (Producer Extends Consumer Super) principle.

Implement a method repot that removes plants from one bed and inserts it in another. Make sure that you can repot from a flower bed to a plant bed, but not vice versa.

1. Add a remove function to PlantBed
2. Implement the utility method repot in a utility class PlantBedUtility, use the appropriate bounds. Why should this class be declared abstract and have a private constructor?

Remark: the above UML diagram for the utility method does not include any bounds but you need some (PECS!) -- the compiler is unable to capture the types if you implement the method strictly as described in the UML!