Sadegh Aliakbary

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Agenda interface Multiple Inheritance 3JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

Abstract Example 4JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

Abstract Method All subclasses have the method But we can not implement the method in super-class So why we define it in super-class? Polymorphism 5JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

Interface Sometimes we have an abstract class, with no concrete method interface : pure abstract class no implemented method 6JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

Interface 7JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

Interface All the methods are implicitly abstract No need to abstract specifier All the methods are implicitly public No need to public specifier 8JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

Interface Implementation Some classes may inherit abstract classes Some classes may implement interfaces Is-a relation exists If a class implements an interface But does not implement all the methods What will happen? The class becomes an abstract class 9JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

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Multiple Inheritance in Java A class can inherit one and only one class A class may implement zero or more interfaces 11JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

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A Question Why multiple inheritance is not supported for classes? Why multiple inheritance is supported for interfaces? 13JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

What About Name Collision? 14 The return types are incompatible for the inherited methods B.f(), A.f() JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

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Interface Extension Interfaces may inherit other interfaces Code reuse Is-a relation 16JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

Interface properties No member variable Variables : implicitly final and static Usually interfaces declare no variable Only operations are declared No constructor Why? 17JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

Example 18JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

Interfaces Applications Pure Abstract classes Describe the design The architect designs interfaces, the programmer implements them Only interfaces are delivered to code consumers More powerful inheritance and polymorphism 19JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

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Quiz! 22JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

References Compiler Error A a; B b; C c; D d; c = d; d = c; b = d; d = b; a.f(); 23 d = new D(); d = new E(); c= new E(); b = new E(); a = b; b.f(); OK JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source

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