// interfaces/nesting/NestingInterfaces.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// {java interfaces.nesting.NestingInterfaces}
package interfaces.nesting;

class A {
 interface B {
 void f();
 }
 public class BImp implements B {
 @Override
 public void f() {}
 }
 private class BImp2 implements B {
 @Override
 public void f() {}
 }
 public interface C {
 void f();
 }
 class CImp implements C {
 @Override
 public void f() {}
 }
 private class CImp2 implements C {
 @Override
 public void f() {}
 }
 private interface D {
 void f();
 }
 private class DImp implements D {
 @Override
 public void f() {}
 }
 public class DImp2 implements D {
 @Override
 public void f() {}
 }
 public D getD() { return new DImp2(); }
 private D dRef;
 public void receiveD(D d) {
 dRef = d;
 dRef.f();
 }
}

interface E {
 interface G {
 void f();
 }
 // Redundant "public":
 public interface H {
 void f();
 }
 void g();
 // Cannot be private within an interface:
 //- private interface I {}
}

public class NestingInterfaces {
 public class BImp implements A.B {
 @Override
 public void f() {}
 }
 class CImp implements A.C {
 @Override
 public void f() {}
 }
 // Cannot implement a private interface except
 // within that interface's defining class:
 //- class DImp implements A.D {
 //- public void f() {}
 //- }
 class EImp implements E {
 @Override
 public void g() {}
 }
 class EGImp implements E.G {
 @Override
 public void f() {}
 }
 class EImp2 implements E {
 @Override
 public void g() {}
 class EG implements E.G {
 @Override
 public void f() {}
 }
 }
 public static void main(String[] args) {
 A a = new A();
 // Can't access A.D:
 //- A.D ad = a.getD();
 // Doesn't return anything but A.D:
 //- A.DImp2 di2 = a.getD();
 // Cannot access a member of the interface:
 //- a.getD().f();
 // Only another A can do anything with getD():
 A a2 = new A();
 a2.receiveD(a.getD());
 }
}