An important technique in the study of Object-Oriented Design is the use of delegation to replace class inheritance. A systematic approach for this transformation was presented in Lectures 4 and 5. Apply this approach to the program Resources à Assignments à Delegation.java. This program defines classes A, B, C, D, E, and F. The result of your transformation should be definition of classes called A2, B2, C2, D2, E2, and F2 which correspond to classes A, B, C, D, E, and F respectively, but do not make use of class inheritance. The original program and the transformed program, when executed, should produce the same results for the given test cases.
A systematic approach involves the following steps:
1. Define an interface hierarchy with interfaces IA, IB, IC, ID, IE, and IF based upon classes A, B, C, D, E, and F. (Optimize the interfaces to avoid redundancy.)
2. Define new classes A2, B2, C2, D2, E2, and F2 which implement IA, IB, IC, ID, IE, and IF respectively.
3. Set up the delegation hierarchy, define delegation methods, and provide a translation for every protected abstract method.
4. Translate the pseudo-variables this and super as this2 and super2 respectively. Access superclass attributes by ‘super2-chaining’, e.g., super2.super2. …
5. In the translated program, you will also need to define two constructors for every non-leaf non-abstract class of the original class hierarchy, i.e., for classes B2 and D2.
The file Delegation.java contains the definitions of classes A … F and also contains two tester classes called Delegation and Delegation2. It also contains the outline of the classes A2 … F2. Define the interfaces IA … IF and the classes A2 … F2 in the same file.
Run both test cases through JIVE and save the object and sequence diagrams in files named
A1_Delegation_obj.png and A1_Delegation_seq.png (for the first test case) and
A1_Delegation2_obj.png and A1_Delegation2_seq.png (for the second test case). For object diagrams, choose ‘Objects with Tables’. For sequence diagrams, choose ‘Expand Lifelines’.
Important: Credit will be given only if the transformation is done in a systematic way. An ad hoc translation that produces correct results is not an acceptable solution for this assignment.
End of Assignment 1 Part2
