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Advanced Programming in Java Sadegh Aliakbary Sharif University of Technology Fall 2010
Advanced Programming in Java
Sadegh AliakbarySharif University of Technology
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AgendaInitializationFinal methods and classesAbstract method and classes
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Review of Polymorphism
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Review of Polymorphism
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Hint on Array Initialization
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InitializationThere are different ways for initialization of
variablesVariable declaration initializationConstructorInitialization block
Guarantees that certain operations occur regardless of which explicit constructor is called
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Static InitializationStatic variables are initiated per class
When class is loadedVariable declaration initializationStatic block
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Order of initializationOnce per class
Static variable declarationStatic block
Once per objectvariable declarationInitialization blockConstrictor
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Final MethodsYou can not override final methods Static method binding for final methodsPrivate methods are implicitly finalStatic methods are implicitly final
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Final VariablesYou can define variables as final
The value of final variable will remain constant
You can not change the value of final variables
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Final Variables
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Final ClassesYou can not inherit from final classesNo class can extend final classes
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Final ReviewFinal data
ConstLocal variablesMethod parametersMember variablesPrimitives constant valuesObjects constant references
A compile-time constant that won’t ever change
A value initialized at run time that you don’t want changed
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Final Review (2)Final Methods
No override Final Class
No sub-class
final keyword on data Different from final classes & methods
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Final Review (3)
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Finalism and PerformanceFinal methods can be invoked inline Compiler can bind final methods statically
Static bindingIt is now discouraged to use final to try
to help the optimizerEspecially with Java 6
Don’t worry about performanceJava optimizer
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Abstract MethodsRemember Shape classes
getArea()draw()
Remember Animals Talk()getName() : not abstract
We can implement these methods by simple dummy operations
Better way : abstract methods
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Abstract Methods (2)abstract method : no implementationA class containing abstract methods: an
abstract classYou can not instantiate abstract classesIf a sub-class do not implement the abstract
methodIt will be abstract too
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Animal Example
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Animal Example (2)
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Quiz!
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Result:Where am I?Animal(String name)I am a catCat(String name)Where am I?Animal(String name)I am a dogDog(String name)Maloos: Meowww!Fido: Hop! Hop!
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