Extra 9. Software design patterns

Tasks

• General intro
• TODO #1
• TODO #2
• More information

Extra 9 exercise: Software design patterns

General intro

1. Review presentation

2. Review package jtm.extra09

3. Implement necessary classes and methods for Crocodile Game.

CrocodileGame contains 2D Board with cells and List of Crocodiles.

Look at CrocodileGame.png for system design.

NOTE: Board of the game is already implemented and its design shouldn't be changed!

TODO #1

1. Implement Crocodile interface with two different classes CrocodileSimple and CrocodileGreedy
   1. MoveStrategy of CrocodileSimple should be implemented in MoveSimple class
   2. MoveStrategy of CrocodileGreedy should be implemented in MoveGreedy class

Crocodiles are positioned on upper left corner of the field, if there is only one cell in board,
neither crocodile need to move at all, but it can eat candy, if it exists.

MoveSimple strategy covers only first row and last column of the board. e.g.

MoveGreedy strategy covers all cells of the board and eats all candies.
Movement always starts and ends on X axis, e.g.

If board has even number of rows, greedy crocodile walks on the last row twice:

Game board has following valid cell values:

○ — empty cell
● — cell with candy
◎ — cell with crocodile footstep

when crocodile gets on to cell with candy ●, it eats this candy after
crocodile leaves cell, it leaves footstep in the cell ◎

CrocodileGame is built using factory class GameFactory which has
setBoard(Board board) and addCrocodile(String crocodileType) methods.

TODO #2

Implement setBoard(Board board) and addCrocodile(String crocodileType) methods
to build CrocodileGame with lazy initialization.

More information

• The 7 Most Important Software Design Patterns
• Software antipatterns