// 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());

}

}