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interfaces in java

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interfaces in java

Mar 8th, 2006

Hey can any body help in this matter:

interface with in interface :

ex: interface ee
{
interface rr{
void ere();
}
}

how to implement the ere method :

please sugesst me

Regards

Saranga

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hooknc

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Re: interfaces in java

Mar 8th, 2006

An interface doesn't actually implement any behavior. It only defines behavior.

So if you define a method called print1() the code for printing out a 1 would not actually be in the interface class. The behavior would have to be defined by a class that implements the interface.

Interface:

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
public interface Print1
{
  public void print1();
}
public interface Print1
{
  public void print1();
}

Implementing class:

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
public class ExampleClass implements Print1
{
  public void print1()
  {
    System.out.println("print 1");
  }
}
public class ExampleClass implements Print1
{
  public void print1()
  {
    System.out.println("print 1");
  }
}

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Re: interfaces in java

Mar 9th, 2006

Thanks for u suggestion,

But i would lilke to know , if there exist an interface , with in that an interface there exist an another interface ..... in that an method is there .if that inner interface is an static than how u will implement . that method .............

•

Originally Posted by hooknc

An interface doesn't actually implement any behavior. It only defines behavior.

So if you define a method called print1() the code for printing out a 1 would not actually be in the interface class. The behavior would have to be defined by a class that implements the interface.

Interface:
Help with Code Tags

Java Syntax (Toggle Plain Text)
public interface Print1
{
  public void print1();
}
public interface Print1 { public void print1(); }
Implementing class:
Help with Code Tags

Java Syntax (Toggle Plain Text)
public class ExampleClass implements Print1
{
  public void print1()
  {
    System.out.println("print 1");
  }
}
public class ExampleClass implements Print1 { public void print1() { System.out.println("print 1"); } }

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hooknc

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Re: interfaces in java

Mar 9th, 2006

Since an Interface has no behavior it cannot be a container and therefore it cannot contain another interface. Now, a Interface can define behavior that says its Implementing class can return a different Interface.

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
public interface A
{
  public B getB();
}
 
 
public interface B
{
  public static String exampleStaticMethod();
}
public interface A
{
  public B getB();
}


public interface B
{
  public static String exampleStaticMethod();
}

Then its easy to call the static method on B.

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
public static void main(String[] args)
{
  A a = new ImplementationOfA();
  a.getB().exampleStaticMethod();
}
public static void main(String[] args)
{
  A a = new ImplementationOfA();
  a.getB().exampleStaticMethod();
}

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Re: interfaces in java

Mar 9th, 2006

Actually, with an interface I believe you can extend as many interfaces as you like.

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hooknc

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Re: interfaces in java

Mar 9th, 2006

Well, you can extend (is a) yes, but an Interface cannot contain (has a) another Interface.

I feel as thought containing another Object is behavior and Interfaces don't have any behavior of their own. The do define behavior, but they don't implement any behavior.

Finally, an Interface can only have one parent that it extends.

(I'm positive you know all this s_c, just hoping to clarifying for all the kiddies.)

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Re: interfaces in java

Mar 9th, 2006

It's confusing stuff. What I think is weird is how an interface can extend as many interfaces as it wants, but a regular class can only extend one..

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Re: interfaces in java

Mar 9th, 2006

•

Originally Posted by hooknc

Finally, an Interface can only have one parent that it extends.

I stand corrected. server_crash is correct. An interface and Extend any number of interfaces. This is quite a shock to me.

Defining an Interface

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Re: interfaces in java

Mar 9th, 2006

I didn't meant to correct you... Actually I didn't even know you posted that

That's just one of the things I find really weird about interfaces and it took me a while to grasp it. I always thought it was, 'you extend classes with special functionality', but 'implement interfaces'. I guess it's just different when you're talking about interfaces. Oh well, I don't use them very often.