Interfaces Presented By Parag Shah http://www.adaptivelearningonline.net

Agenda Java and multiple inheritance Declaring interfaces Using interfaces

Java and multiple inheritance

Declaring interfaces

Using interfaces

Java And Multiple Inheritance - 1 Java does not have multiple inheritance Inheritance gives us two things Code reuse Ability to represent the object polymorphically as the super type

Java does not have multiple inheritance

Inheritance gives us two things

Code reuse

Ability to represent the object polymorphically as the super type

Java And Multiple Inheritance - 2 Code reuse in multiple inheritance is risky The ability to represent a class polymorphically as a type other than the superclass may be useful Interfaces allow the latter but not the former

Code reuse in multiple inheritance is risky

The ability to represent a class polymorphically as a type other than the superclass may be useful

Interfaces allow the latter but not the former

Interfaces Interfaces are defined with the interface keyword Interfaces do not have any code All attributes are public static final public interface Ignorable { public boolean isValid(); }

Interfaces are defined with the interface keyword

Interfaces do not have any code

All attributes are public static final

public interface Ignorable {

public boolean isValid();

}

Implementing An Interface Any class can implement an interface Use the implements keyword A class can implement multiple interfaces The class must implement all the methods declared in the interface See [biz.adaptivesoftware.examples.interfaces]

Any class can implement an interface

Use the implements keyword

A class can implement multiple interfaces

The class must implement all the methods declared in the interface

See [biz.adaptivesoftware.examples.interfaces]

Marker Interfaces Some interfaces are used as flags for the JVM Cloneable Serializable SingleThreadModel

Some interfaces are used as flags for the JVM

Cloneable

Serializable

SingleThreadModel

Summary Interfaces allow us to polymorphically represent a class as types across inheritance trees Interfaces are implemented with the implements keyword Do not CREATE interfaces for non standard use such as marker interfaces

Interfaces allow us to polymorphically represent a class as types across inheritance trees

Interfaces are implemented with the implements keyword

Do not CREATE interfaces for non standard use such as marker interfaces