CSSE2002/7023 Semester 1 2020 Final Exam Marking Criteria Question 1 N/A – used for starting assumptions during exam Question 2 false false false true Question 3 [1, 2, 3, 3, 4, 5] Question 4 Coder? Question 5 1234 5678 Question 6 The method z would throw an exception. Question 7 5 Question 8 A r1 = (A)c; B r2 = (B)d; D r6 = (D)d; Question 9 Subclass B uses protected data member d from superclass and modifies protected datamember i from superclass. It also overrides doOther to change its behaviour, and allows a downcall. A, C and D are as tightly coupled as possible. 12 Marks • 3 marks for identifying overall tight coupling • 3 marks for a very general explanation • 3 marks for the links between methods & how this increases coupling o Need example(s) for more than 1 mark of this o e.g. cycle between C & A o e.g. “forwarding of behaviour” A.doSomething just calling c.doC() • 1 marks for dependency on instances that need init out of constructor (C & D) • 1 marks for identifying there is inheritance coupling o Should mention use of protected method ▪ d.doD • 1 marks for all classes use all others that are possible o i.e. A uses B,C,D, B uses A,C,D, etc... • Deduction for major contradictions of previous good answers o Half of the previously given mark o Full mark deduction for single sentence contradiction of premise (high/low) Question 10 0 C D Question 11 6 marks for explanation of MVC. • 2 Marks for Explain idea of model representing state/data • 2 Marks for Explain idea of UI providing user interaction o Separation of View & Controller - can be implicit • 2 Marks for Explain how it all works together o How elements interact/communicate. o Changes to the interface reflected in the model and vice versa 4 marks for describing the benefit of the MVC approach. • Only need to describe one benefit (i.e. “purpose” from question) • But need to clearly explain the reason for the approach (the why), not just say that it provides separation between M, V & C o 2 marks for identifying at least one purpose of MVC o 2 marks for reasonable explanation of purpose or value of providing the separation Question 12 4 marks each question • 1 mark for identifying if it meets LSP or not • 2 marks for a correct general explanation o Has the pre/postcondition been weakened/strengthened • 1 mark for detail o Wider range of inputs; > changed to >=; etc. 1. B wrt A • Satisfies LSP • Precondition weaker (less restrictive), postcondition stronger (more restrictive). • variance <= 1 weaker than variance < 1, • Math.abs(values[i] - targets[i]) < variance stronger than Math.abs(values[i] - targets[i]) <= variance 2. C wrt A • Violates LSP • Precondition stronger (more restrictive), postcondition unchanged • variance > 0 stronger than variance >= 0 3. D wrt A • Satisfies LSP • Precondition weaker (less restrictive), postcondition unchanged • values.size() <= targets.size() weaker than values.size() == targets.size() Question 13 Black Box Tests: 11 marks • Both lists are empty (2 marks), or size of 1 (1 mark) • Values & targets same size (1 mark) • Values.size() < targets.size()(1 mark) • Variance is 0 (2 marks) • Variance is valid value (1 mark) • Output is empty (2 marks) • Output has results (2 marks) o A value in “targets” is larger than corresponding value in “values” - should justify o A value in “values” is larger than corresponding value in “targets” • -½ mark for each incorrect justification (only for inputs that are contributing to marks) White Box Tests: 7 marks (1 mark each) Question 14 JavaDoc: 7 marks • 1 mark for Description • 1 mark for params • 1 mark for return • 2 marks for pre condition o 1 for string can’t be null (or implicitly via str.length()) o 1 for bounds check on strLengthToTest (general) • 2 marks for post condition o 2 marks for restating return clearly and unambiguously Code: 9 marks Base Case: • 1 mark for base case exists • 1 mark for condition • 1 mark for correct return Recursive Case: • 2 mark for recursive case exists o 1 for consonant case o 1 for vowel case • 1 mark for reducing input (not infinite recursion) • 1 mark for returning result (i.e. deduct if “return” missing) • 2 marks for adding or not adding in recursive return: o 1 mark for adding to result (i.e. return 1 + …) in the consonant case o 1 mark for not adding to result in return in the vowel case static int totalConsonantsRecursive(String str, int strLengthToTest) { if (strLengthToTest == 1) { if(isConsonant(str.charAt(0))) return 1; else return 0; } if(isConsonant(str.charAt(strLengthToTest - 1))) return totalConsonantsRecursive(str, strLengthToTest - 1) + 1; else return totalConsonantsRecursive(str, strLengthToTest - 1); } Question 15 8 marks for implementation of generic Kennel. • 2 for generic type parameter o 1 for just
o 2 for correct restriction on Pet • 1 for generic list member variable • 1 for instantiating the list (even if list variable is not generic) • 2 for has addPet method or similar o 1 for Exists o 1 for Has generic param • 2 for has retrievePet o 1 for Exists incl. Must have/use int param o 1 mark for generic return value 6 marks for Non-Generic Explanation • 2 marks for explanation of Kennel having a collection of Pets o i.e. List • 2 marks for explanation that a generic Kennel has the additional restriction of collections of only specific subtypes of Pets. o i.e. Kennel, Kennel • 2 marks for rationale of the restriction. ▪ Ensure that the class/method is operating on instances with appropriate methods/data. o Saves manual checking of types in runtime logic o Benefits of animal-specific kennels (i.e. real world kennels) package generics; import java.util.ArrayList; import java.util.List; class Pet { } class Cat extends Pet { } class Dog extends Pet { } public class Kennel { private List pets; public Kennel() { pets = new ArrayList<>(); } public void addPet(T pet) { pets.add(pet); } public T getPet(int petLocation) { return pets.get(petLocation); } public static void main(String... args) { Kennel cattery = new Kennel<>(); Kennel dogKennel = new Kennel<>(); cattery.addPet(new Cat()); dogKennel.addPet(new Dog()); } } 欢迎咨询51作业君
