java 内部类的继承

因为内部类的构造器必须连接到指向其外部类对象的引用. 因为在继承内部类的时候那个指向外部类对象的"秘密的"引用必须被初始化,而在导出类中不再存在可连接的默认对象,要解决这个问题必须用特殊的语法来明确说清它么之间的关联:

//: innerclasses/InheritInner.java
// Inheriting an inner class.

class WithInner {
  class Inner {}
}

public class InheritInner extends WithInner.Inner {
  //! InheritInner() {} // Won't compile
  InheritInner(WithInner wi) {
    wi.super(); //必须
  }
  public static void main(String[] args) {
    WithInner wi = new WithInner();
    InheritInner ii = new InheritInner(wi);
  }
} ///:~