Transcript Advanced Object Oriented Systems

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Advanced Object Oriented
Systems
(CM0318)
Introductory Lecture
(Last modified: 28th January 2002)
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Suggested linked list
implementation
• 2 classes: MyLinkedList and MyLink
(NB actually Java provides a class
LinkedList)
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MyLinkedList
• instance variables:
– MyLink first
– MyLink last
– int size
• methods:
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–
–
–
–
MyLinkedList()
void add(Object element)
Enumeration elements()
int size()
...
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MyLink
• Instance variables
– MyLink next;
– Object element;
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Suggested Deptl. Info. System
implementation
• Classes include:
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–
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Lecturer
Student
Module
(Department)
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Lecturer
• instance variables:
– String name (or could be split up into parts)
– Vector modules_given
• methods:
– void add_module(Module m)
– Enumeration all_modules() (or Vector?)
– (optionally things to set the name, etc., which
could then be made private)
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Student
• instance variables
– String name (or could be split up into parts)
– int student_number (or should it be a String?)
– Vector modules_taken
• methods
– things to add a module, etc., similar to Lecturer
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Module
• instance variables
– String module_code
– String module_title
• methods
– accessors (set code, etc.)
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Department
• instance variables
– Vector lecturers
– Vector students
– Vector available_modules
• methods
– Vector lecturer_names() (or Enumeration?)
– Vector all_students()
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Note Well
• Always more than one way to model a
problem!
• Because of Java’s type system, collections
like Vectors are horrible to use - but better
than nothing! E.g. to iterate through the
lecturers’ names you’ll need code like this:
Enumeration e = lecturers.elements();
while (e.hasMoreElements()) {
do_something_with(
((Lecturer) e.nextElement()).name);}
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Topics
• Why OO?
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–
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intuitive
modelling
software quality
reuse
• Features of OO that give these qualities
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Java
• Using the libraries
• Modelling non-trivial problems
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Design
• ACJ:
– Design by contract
• AIA:
– Methodologies
– Communicating design
• CRC Cards
• UML
– Design patterns
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Other OO languages
• Dynamically typed languages
– Smalltalk
– Self (classless!!)
• Statically typed languages
– C++
– Eiffel (NB supports design by contract)
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Building systems interactively
• ACJ:
– The Smalltalk programming environment
approach
• AIA:
– The CASE approach
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Distributed objects - CORBA
• Language & platform independence
• Wrapping legacy applications
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Implementation of OO languages
• Memory management
• Virtual machines
• Bottlenecks & clever ideas!!