Interface

[Abhi vijay]

Can the private,protected access modifiers be applied to Interfaces. How do they restrict access??

[Wouter Oet]

No they can not. Only public and default are allowed. They restrict access the normal way. But why not try for yourself or look it up in the Java Language Specification?

[marc weber]

If you check the JLS, you will see that private and protected can be applied to (nested) interfaces...

The access modifiers protected and private pertain only to member interfaces within a directly enclosing class...

[NagarajGoud uppala]

For interfaces we can not apply private,protected.It must always declare as public because interface is method prototype that is all the methods are 100% abstract.the method body will be implemented in the implementation classes.

if your using private, the methods can't accessible to other classes.so we can't implement those methods in the implementation classes.

coming on to protected,the methods have accessibility to subclasses but any implementation class is not subclass to any interface.

so interface-always public

[Abhi vijay]

Thanks..nagraju.

[marc weber]

Originally posted by nagaraju uppala:
For interfaces we can not apply private,protected...

Again, that's not exactly true. A nested interface can be private or protected. (See the JLS link above.)

[marc weber]

For example...

class Enclosing {
  [B]private interface[/B] PrivateEye {
    void meth();
  }
  
  class Inner implements PrivateEye {
    public void meth() {
      System.out.println("Methodonia.");
    }
  }
  
  public static void main(String[] args) {
    Enclosing.PrivateEye myEye = new Enclosing().new Inner();
    myEye.meth();
  }
}

[Abhi vijay]

That means public is the only access modifier that can be applied to a top-level Interface. For nested Interfaces, public,private,protected can be applied. Right?

[Abhi vijay]

 class Enclosing
{
   protected interface PrivateEye
  {
    void meth();
  }
 
  class Inner implements PrivateEye
  {
    public void meth()
    {
      System.out.println("Methodonia.");
    }
  }
 
  public static void main(String[] args)
  {
    Enclosing.Inner myEye = new Enclosing().new Inner();
    myEye.meth();
    new Bo().meth();
  }
}
 

class Bo extends Enclosing.Inner implements Enclosing.PrivateEye
{
public void meth()
{
System.out.println("SUBCLASS");
}
}
 

In the above example I am getting compiler error. What is the right way of extending an Inner class?

[Ankit Garg]

Abhi the code that you gave tries to extend a non-static inner interface. You need an instance of the enclosing class to do that. This is allowed with the other non-static inner class as it has an enclosing class instance. But to implement it outside the enclosing class or in static member classes of the enclosing class, you need to have an explicit super call in the constructor with an enclosing class instance. So use this code

class Enclosing
{
   protected interface PrivateEye
  {
    void meth();
  }
 
  class Inner implements PrivateEye
  {
    public void meth()
    {
      System.out.println("Methodonia.");
    }
  }
 
  public static void main(String[] args)
  {
    Enclosing.Inner myEye = new Enclosing().new Inner();
    myEye.meth();
    new Bo().meth();
  }
}
 
 
class Bo extends Enclosing.Inner implements Enclosing.PrivateEye
{
[B]Bo()
{
new Enclosing().super();
}[/B]
public void meth()
{
System.out.println("SUBCLASS");
}
}

[Abhi vijay]

Thanks Ankit