內部類的繼承

• 因為內部類的構造器必須連線到指向其外圍類物件的引用，所以在繼承內部類的時候，會很複雜。問題在於：那個指向外圍類物件的引用必須被初始化，而在匯出類中不再存在可連線的預設物件。
  

內部類可以被覆蓋嘛？

package com2002;

/**
 * Created by Panda on 2018/6/11.
 */
class Egg {
    private Yolk yolk;

    protected class Yolk {
        public Yolk() {
            System.out.println("Egg.Yolk()");
        }
    }

    public
 
 Egg() {
        System.out.println("New Egg()");
        yolk = new Yolk();
    }
}

public class BigEgg extends Egg{
    public class Yolk {
        public Yolk() {
            System.out.println("BigEgg Yolk()");
        }
    }

    public static void main(String[] args) {
        new BigEgg();
    }
    /**
     * New Egg()
     Egg.Yolk()
     */
 

    //當繼承了某個外圍類的時候，內部類並沒有發生什麼特別的變化。這兩個內部類是完全獨立的兩個實體
    //各自在自己的名稱空間內
}

package com2002;

/**
 * Created by Panda on 2018/6/11.
 */
class Egg2{
    protected class Yolk{
        public Yolk(){
            System.out.println("Egg2.Yolk()");
        }
        public void f(){
            System.out.println("Egg2.Yolk.f()"
 
);
        }
    }
    private Yolk yolk=new Yolk();
    public Egg2(){
        System.out.println("New Egg2()");
    }
    public void insertYolk(Yolk yolk){this.yolk=yolk;}
    public void g(){yolk.f();}
}
public class BigEgg2 extends Egg2{
    public class Yolk extends Egg2.Yolk{
        public Yolk(){
            System.out.println("BigEgg2.Yolk()");
        }
        public void f(){
            System.out.println("BigEgg2.Yolk.f()");
        }
    }
    public BigEgg2(){insertYolk(new Yolk());}

    public static void main(String[] args) {
        Egg2 egg2=new BigEgg2();
        egg2.g();
    }
    /**
     * Egg2.Yolk()
     New Egg2()
     Egg2.Yolk()
     BigEgg2.Yolk()
     BigEgg2.Yolk.f()
     */
}