Advanced Programming in Java

1. Advanced Programming in Java SadeghAliakbary Sharif University of Technology Fall 2010

2. Agenda • Initialization • Final methods and classes • Abstract method and classes Sharif University of Technology

3. Review of Polymorphism Sharif University of Technology

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5. Review of Polymorphism Sharif University of Technology

6. Hint on Array Initialization Sharif University of Technology

7. Initialization • There are different ways for initialization of variables • Variable declaration initialization • Constructor • Initialization block • Guarantees that certain operations occur regardless of which explicit constructor is called Sharif University of Technology

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9. Static Initialization • Static variables are initiated per class • When class is loaded • Variable declaration initialization • Static block Sharif University of Technology

10. Order of initialization • Once per class • Static variable declaration • Static block • Once per object • variable declaration • Initialization block • Constrictor Sharif University of Technology

11. Final Methods • You can not override final methods • Static method binding for final methods • Private methods are implicitly final • Static methods are implicitly final Sharif University of Technology

12. Final Variables • You can define variables as final • The value of final variable will remain constant • You can not change the value of final variables Sharif University of Technology

13. Final Variables Sharif University of Technology

14. Final Classes • You can not inherit from final classes • No class can extend final classes Sharif University of Technology

15. Final Review • Final data • Const • Local variables • Method parameters • Member variables • Primitives  constant values • Objects  constant references • A compile-time constant that won’t ever change • A value initialized at run time that you don’t want changed Sharif University of Technology

16. Final Review (2) • Final Methods • No override • Final Class • No sub-class • final keyword on data • Different from final classes & methods Sharif University of Technology

17. Final Review (3) Sharif University of Technology

18. Finalism and Performance • Final methods can be invoked inline • Compiler can bind final methods statically • Static binding • It is now discouraged to use final to try to help the optimizer • Especially with Java 6 • Don’t worry about performance • Java optimizer Sharif University of Technology

19. Abstract Methods • Remember Shape classes • getArea() • draw() • Remember Animals • Talk() • getName() : not abstract • We can implement these methods by simple dummy operations • Better way : abstract methods Sharif University of Technology

20. Abstract Methods (2) • abstract method : no implementation • A class containing abstract methods: an abstract class • You can not instantiate abstract classes • If a sub-class do not implement the abstract method • It will be abstract too Sharif University of Technology

21. Animal Example Sharif University of Technology

22. Animal Example (2) Sharif University of Technology

23. Quiz! Sharif University of Technology

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27. Result: • Where am I? • Animal(String name) • I am a cat • Cat(String name) • Where am I? • Animal(String name) • I am a dog • Dog(String name) • Maloos: Meowww! • Fido: Hop! Hop! Sharif University of Technology

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