Understanding interfaces

[Pratik D mehta]

we declare a interface and declare methods in it -
Than this interface is implemented by a class
I this class both the methods of the interfaces are defined
But why do they have to be specified as public to work ?

[David Newton]

Because interface methods are intrinsically public, and the point of an interface is to define an external contract.

[Eoin Brosnan]

Pratik D mehta wrote: we declare a interface and declare methods in it -
Than this interface is implemented by a class
I this class both the methods of the interfaces are defined
But why do they have to be specified as public to work ?

Why are the methods in class that implements the interface forced to be public? That's pretty easy to explain.

  public interface TV{
	  public boolean onOff();
}

public class BrandedTV implements TV{

	@Override
	private boolean onOff() {
		// TODO Auto-generated method stub
		return false;
	}
	
	
	
}

public class randomClass{

   public static void main(String[] args){
		TV new3DHDsuperduperTV = new BrandedTV();
        new3DHDsuperduperTV.onOff(); //cannot be accessed

	}

}
  

By making the method private it's as if it doesn't exist- i.e it's like the interface wasn't implemented.

[Pratik D mehta]

this is the situation I wanted to know about

[code]  interface TV{
	   boolean onOff();
}

public class BrandedTV implements TV{

	// Why do we have to write public for boolean method
	public boolean onOff() {
				return false;
	}
	
	
	
}

public class randomClass{

   public static void main(String[] args){
		TV new3DHDsuperduperTV = new BrandedTV();
        new3DHDsuperduperTV.onOff(); 

	}

}
  

[/code]

[Manjusha Muraleedas]

Why do we have to write public for boolean method

You have already got the answer from David Newton .

[Manjusha Muraleedas]

Why do we have to write public for boolean method

You have already got the answer from David Newton

Because interface methods are intrinsically public. Classes are not.

[Pratik D mehta]

David Newton wrote:Because interface methods are intrinsically public, and the point of an interface is to define an external contract.

I actually didn't get this can you please explain in a more simpler way .

[Manjusha Muraleedas]

you need to have a basic understanding of java interface.

The following tutorial may help you...Interface Tutorial

[Abimaran Kugathasan]

Every methods in interface are implicitly public whether you defined or not. And if you implements the interface, you should override the method in your class. In order to override the method, you need to follow the overriding rules.

And the reason for every methods in the interface are public, is explained by David in his post.

[When overriding a method, you can implement the method with less restriction. public is the least restricted access modifier, so you should implement with public modifier.]

Is it clear?

[Pratik D mehta]

Abimaran Kugathasan wrote:Every methods in interface are implicitly public whether you defined or not. And if you implements the interface, you should override the method in your class. In order to override the method, you need to follow the overriding rules.

And the reason for every methods in the interface are public, is explained by David in his post.

[When overriding a method, you can implement the method with less restriction. public is the least restricted access modifier, so you should implement with public modifier.]

Is it clear?

Thankyou very much abimaran for this explanation. I enjoy discussing on this forum

[Abimaran Kugathasan]

me too. I'm addict to this forum!