COM 379 Exam Revision Lecture

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COM 379Exam Revision Lecture

• james.malone_at_sunderland.ac.uk

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Exam Format

• Thursday, 27th January
• 600-900
• RV113
• 14 Question in total, Three sections
• OO Programming
• OO Theory
• OO Practice
• Answer TEN questions, with at least TWO from each
  section

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Exam Topics

• Primitive Types
• Reference Types (including Object class)
• Access Modifiers
• Inner Classes
• Iterators
• Interfaces
• Threads
• Exceptions
• Constructors Constructor Chaining

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Exam Topics

• Interface Segregation Principle (ISP)
• Meyers Design By Contract
• Open-Closed Principle (OCP)
• Liskov Substitution Principle (LSP)
• Dependency Inversion Principle (DIP)
• Single-Responsibility Principle (SRP)
• Bad Software Design (When software smells)
• Encapsulation, Inheritance, Subtype-Polymorphism
  Abstraction

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Exam Topics

• UML (eg Class diagrams, state charts, use cases,
  interaction diagrams, etc.)
• Design Patterns
• Modelling Classes
• Requirements Analysis
• Software Maintainability

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Example Questions

• Name and describe the 8 primitive types
• Boolean, char, etc.
• How is a type conversion done?
• When is it suitable (think data loss)?
• Describe the three categories of reference data
  types (that inherit from Object).
• Class instance, array, interface

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Example Questions

• Name four methods Object class provides
• toString(), clone(), getClass(), equals(), etc.
• How is a class instantiated?
• Simple code
• public Balance currentBalance new Balance()
• What is a static method?
• Method not associated with an instance but
  rather at class level

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Example Questions

• Describe 4 access modifiers
• Remember table!

Accessible to Public Protected Package Private
Defining Class Yes Yes Yes Yes
Class in same package Yes Yes Yes No
Subclass in different package Yes Yes No No
Non-sublcass different package Yes No No No
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Example Questions

• What is an inner class?
• Class within a class
• Static Member class
• Member class
• Local class
• Anonymous class

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Example Questions

• What is an iterator
• Allow processing (step through) of each element
  of a collection
• Sample code might be asked for!
• Iterator myIterator myCollection.iterator()
• while(myIterator.hasNext())
• Object myObject myIterator.next()
• //do something with myObject possibly cast

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Example Questions

• What is an interface?
• a collection of method definitions and constant
  values that define a behaviour
• Replace multiple inheritance more than one
  interface can be inherited.
• Does not implement methods however
• What is a thread?
• a separate stream of execution that takes place
  simultaneously with and independently of
  everything else remember Thread class and
  Runnable interface

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Example Questions

• What is an Exception? How is it dealt with in
  Java?
• An Exception is an object created and thrown when
  an exceptional circumstance (usually caused an
  erroneous condition) occurs
• Java try, catch, throw, finally

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Example Questions

• What is a constructor?
• General description, code example might help
• What is constructor chaining?
• A child object constructor always first needs to
  construct its parent (which in turn calls its
  parent constructor.). Can also be manufactured
  by enforcing other constructors to be called
  within the same or parent classes

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Example Questions

• Describe the Interface Segregation Principle
  (ISP)?
• Many client specific interfaces (narrow) are
  better than one general purpose interface
• Fat interfaces lead to inadvertent coupling
• Describe the Liskov Substitution Principle (LSP)?
• Subclasses should be suitable for their base
  classes
• The contract of the base class must be honoured
  by the derived class

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Example Questions

• What is the Open-Closed Principle (OCP)?
• A module (class) should be open for extension but
  closed for modification (originally by Bertrand
  Meyer).
• Classes should be written so that they can be
  extended without requiring the classes to be
  modified.
• To extend the behavior of a system (in response
  to a requested change) add new code, dont modify
  existing code.

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Example Questions

• Describe the Dependency Inversion Principle (DIP)
• Depend upon abstractions. Do not depend upon
  concrete implementations
• High level classes should not depend on low level
  classes.
• Abstractions should not depend upon the details.
• If the high level abstractions depend on the low
  level implementation details, then the dependency
  is inverted from what it should be.

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Example Questions

• Describe the Single-Responsibility Principle
  (SRP)
• A class should have only one reason to change
• A responsibility is a reason for change.
• The responsibilities of a class are axes of
  change. If it has two responsibilities, they are
  coupled in the design, and so have to change
  together.

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Example Questions

• Meyers Design By Contract
• class method must satisfy two rules
• There are only two ways a routine call may
  terminate either it fulfills its contract or it
  fails to fulfill it.
• If a routine fails to fulfill its contract, the
  current execution of the caller also fails to
  fulfill its own contract.

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Example Questions

• Describe symptoms of bad software design (think
  when software smells)
• The system is rigidhard to change because
  everything has to change at once.
• The system is fragilechanges cause the system to
  break in the strangest of places.
• The system is immobilenot reusable.
• The system is viscousdoing things right is hard.
• The system is needlessly complex.
• The system contains needless repetition.
• The system is opaquehard to understand

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Example Questions

• Describe what is meant by encapsulation
• Diagram might help
• Describe what is meant by inheritance
• Keywords may also help (extends)
• Describe what is meant by subtype-polymorphism
• The ability of an object or operator to refer to
  instances of different classes at run time.

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Example Questions

• How is abstraction achieved in Java?
• Various ways Abstract (keyword) classes,
  interfaces and inhertiance
• Describe a State chart / Use Case Diagram / Class
  Diagram / Interaction Diagram
• Diagram essential key is to remember all
  elements of the diagram

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Example Questions

• Describe one of the following patterns
• Factory Method
• Singleton
• Adapter
• Flyweight
• Proxy
• MVC
• Iterator
• Observer

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Example Questions

• How might you gather and analyze requirements?
  Compare and contrast the approaches.
• Brainstorming, Observation etc.
• Discuss and criticize the design principles the
  authors claim lead to maintainable software
• Design and conquer
• Increase cohesion where possible
• Reduce coupling where possible
• Keep the level of abstraction as high as possible
  
• Increase reusability where possible
• Reuse existing designs and code where possible
• Anticipate obsolescence
• Design for portability
• Design for testability
• Design defensively

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General Advice

• Read through whole paper once work out which
  questions you answer best.
• With 3 hours you have 18 minutes per question
• Good luck!!!