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Thread: what is the use of interfaces and abstract classes?

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    Default what is the use of interfaces and abstract classes?

    I am 5 years experienced in programming in C but Till I cant understand the languages like Java.
    what is the use of using interfaces and abstract class since they do nothing.
    Last edited by sagar474; September 18th, 2011 at 03:11 PM.


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    Default Re: what is the use of interfaces and abstract classes?

    Interfaces are a way to give a data type to an object. Java is strict on data typing compared to c.
    They allow the compiler to verify that a class object has the method(s) required for that data type.
    A common used interface is a listener. The compiler guarantees that any object that says it is a listener will have all the required methods defined by the interface.

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    Default Re: what is the use of interfaces and abstract classes?

    public class Main {
     
     
     
        public static void main(String[] args) {
     
              shape circleshape=new circle();
     
                 circleshape.Draw();
        }
    }
     
     interface shape
     {
         public   String baseclass="shape";
     
         public void Draw();
     
     
     }
     class circle implements shape
     {
     
        public void Draw() {
            System.out.println("Drawing Circle here");
        }
     
     
     }

    both programs do the same!
    public class HelloWorld {
     
     
     
        public static void main(String[] args) {
     
              circle circleshape=new circle();
     
                 circleshape.Draw();
        }
    }
     
     
     class circle 
     {
     
        public void Draw() {
            System.out.println("Drawing Circle here");
        }
     
     
     }

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    Default Re: what is the use of interfaces and abstract classes?

    What's the point?

    Where is the method that takes an argument of type shape?

    void SomeMethod(shape aShape) {
    }

    You could NOT pass an object of the circle class from your second code example to this method. It is not a shape.

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    Default Re: what is the use of interfaces and abstract classes?

    Is interface shape can used as a data-type?
    and where as a circle can not be use as a data type when since it is not implemented shape?

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    Default Re: what is the use of interfaces and abstract classes?

    Both shape and circle are data types.
    And so are Main and HelloWorld data types.

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