ex6.java

Thinking In Java 第四版练习题答案

// innerclasses/Ex6.java
// TIJ4 Chapter Innerclasses, Exercise 6, page 353
/* Create an interface with at least one method, in its own package. Create
* a class in a separate package. Add a protected inner class that 
* implements the interface. In a third package, inherit from your class and
* inside a method, return an object of the protected inner class, upcasting
* to the interface during the return.
*/

/* // in separate package:
* public interface Ex6Interface {
*	String say();
* }
*
* // and in a second package:
* public class Ex6Base {
*	protected class Ex6BaseInner implements Ex6Interface {
*		// need public constructor to create one in Ex6Base child: 
*		public Ex6BaseInner() { }
*		public String say() { return "Hi"; }
*	}
* }
*/ 

import innerclasses.ex6Interface.*;
import innerclasses.ex6Base.*;

public class Ex6 extends Ex6Base {
	Ex6Interface getBaseInner() { 
		return this.new Ex6BaseInner();
	}
	public static void main(String[] args) {
		Ex6 ex = new Ex6();
		System.out.println(ex.getBaseInner().say());
	}	
}