94 lines
2.1 KiB
Java
94 lines
2.1 KiB
Java
// interfaces/nesting/NestingInterfaces.java
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// (c)2021 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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// {java interfaces.nesting.NestingInterfaces}
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package interfaces.nesting;
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class A {
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interface B {
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void f();
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}
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public class BImp implements B {
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@Override public void f() {}
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}
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private class BImp2 implements B {
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@Override public void f() {}
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}
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public interface C {
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void f();
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}
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class CImp implements C {
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@Override public void f() {}
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}
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private class CImp2 implements C {
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@Override public void f() {}
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}
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private interface D {
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void f();
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}
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private class DImp implements D {
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@Override public void f() {}
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}
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public class DImp2 implements D {
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@Override public void f() {}
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}
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public D getD() { return new DImp2(); }
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private D dRef;
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public void receiveD(D d) {
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dRef = d;
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dRef.f();
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}
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}
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interface E {
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interface G {
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void f();
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}
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// Redundant "public":
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public interface H {
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void f();
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}
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void g();
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// Cannot be private within an interface:
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//- private interface I {}
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}
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public class NestingInterfaces {
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public class BImp implements A.B {
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@Override public void f() {}
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}
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class CImp implements A.C {
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@Override public void f() {}
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}
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// Cannot implement a private interface except
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// within that interface's defining class:
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//- class DImp implements A.D {
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//- public void f() {}
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//- }
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class EImp implements E {
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@Override public void g() {}
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}
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class EGImp implements E.G {
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@Override public void f() {}
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}
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class EImp2 implements E {
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@Override public void g() {}
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class EG implements E.G {
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@Override public void f() {}
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}
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}
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public static void main(String[] args) {
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A a = new A();
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// Can't access A.D:
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//- A.D ad = a.getD();
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// Doesn't return anything but A.D:
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//- A.DImp2 di2 = a.getD();
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// Cannot access a member of the interface:
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//- a.getD().f();
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// Only another A can do anything with getD():
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A a2 = new A();
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a2.receiveD(a.getD());
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}
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}
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