【JAVA學習路-think in java】p185：嵌套接口詳解

總結：

• 1、class中允許有private、protected、default、public接口，但interface中的接口只能是public的（隱public，不必聲明）;
• 2、class中的private接口，不能被繼承。所以private接口只能在該class中被實現。
• 3、接口中的函數只能是public、static、abstract、default的，不能是private的;
• 4、在任何情況下，類在繼承接口時，實施接口內的函數時，必須顯式聲明爲public；
• 5、繼承接口時，接口中聲明的函數必須全部給出具體實現（寫出函數體），但該接口中的接口所聲明的函數，可以不必給出具體實現。

 

• package pkg;
  
  import pkg.Aa.Dimple2;
  
  class Aa{
  	
  	//** interface
  	protected interface B{void f();}//PROTECTED interface is allowed in Class
  	interface C{void f();}//default interface is allowed in Class
  	private interface D{void f();}//PRIVATE interface is allowed in Class
  	
  	interface E{
  		interface G{void f();}//The interface member type G can ONLY be PUBLIC
  		interface H{void f();}
  		void g();//only public, abstract, default, static are permitted
  		void g2();
  		static void g3() {System.out.println("Function body is needed here for static method");};
  	}
  
  	//** class
  	class generalClass{//definite a class in a class
  		void f() {System.out.println("f() in generalClass of class Aa");}
  		private void f2() {System.out.println("f2() in generalClass of class Aa");}
  	}
  	class Bimple implements B{
  		 public void f() {System.out.println("f() with public in Bimple");}
  		 //Cannot reduce the visibility of the inherited method from A.B:add public
  	}
  	class Bimple2 implements B{
  		public void f() {System.out.println("f() in Bimple 2 of class Aa");}
  	}
  	class Cimple implements C{
  		public void f() {System.out.println("f() in Cimple of class Aa");}
  	}
  	private class Dimple implements D{
  		public void f() {System.out.println("f() in Dimple of class Aa");}
  	}
  	public class Dimple2 implements D{
  		public void f() {System.out.println("f() in Dimple2 of class Aa");}
  	}
  	
  	//** method
  	public D dRef; // a interface can be defined!
  	public D getD() {//up cast
  		return new Dimple();
  	}
  	
  	public void receiveD(D d) {// interface can be one argument
  		dRef=d;
  		dRef.f();
  	}
  }
  
  
  //  ...  main  ...
  public class p185{
  	
  	//...>>>implements
  	public class Bimple implements Aa.B{//how to implements a interface in one class
  		@Override
  		public void f() {System.out.println("f() in Bimple  of p185 with interface Aa.B");}
  	}
  	public class Cimple implements Aa.C{
  		@Override
  		public void f(){System.out.println("f() in Cimple of p185 with interface Aa.C");}
  	}
  	
  //	public class Dipmle implements Aa.D{//The type Aa.D is not visible
  //		@Override
  //		public void f(){System.out.println("f() in Cimple of class Bimple of p185");}
  //	}
  	public class Eimple implements Aa.E{
  		//The type p185.Eimple must implement the inherited abstract method Aa.E.g() & Aa.E.g2()
  		public void g() {System.out.println("g() in Eimple of p185 with interface Aa.E");}
  		public void g2() {System.out.println("g2() in Eimple of p185 with interface Aa.E");}
  		//Cannot reduce the visibility of the inherited method from Aa.E
  	}
  	public class EGimple implements Aa.E.G{
  		//The type p185.EGimple must implement the inherited abstract method Aa.E.G.f()
  		public void f() {System.out.println("f() in Bimple  of p185 with interface Aa.E.G");}
  		//Cannot reduce the visibility of the inherited method from Aa.E
  	}
  	protected class EHimple implements Aa.E.H{
  		public void f() {System.out.println("f() in Bimple  of p185 with interface Aa.E.H");}
  	}
  	public class Eimple2 implements Aa.E{
  		public void g() {System.out.println("g() in Eimple2 of p185 with interface Aa.E");}
  		public void g2() {System.out.println("g2() in Eimple2 of p185 with interface Aa.E");}
  		class EGimple2 implements Aa.E.G{
  			public void f() {System.out.println("f() in EGimple2 of interface Aa.E.G of Interface Aa.E in p185");}
  		}
  	}
  	
  	// main function
  	public static void main(String[] args) {
  		Aa obj=new Aa();
  		obj.receiveD(obj.getD());
  //		Aa.D  x2=obj.getD();//The type Aa.D is not visible
  //		Aa.Dimple x3=obj.getD();// cannot convert from Aa.D to Aa.Dimple
  //		obj.getD().f();//The type Aa.D is not visible
  //		Dimple d1=new Dimple();//Dimple cannot be resolved to a type
  //		Aa.Dimple2 d2=new Aa.Dimple2();
  		//No enclosing instance of type Aa is accessible.
  		//Must qualify the allocation with an enclosing instance of type Aa (e.g. x.new A() where x is an instance of Aa).
  	}
  }