如何在接口中实现嵌套的非静态类？

Question

有这个课

public abstract class Mother{
  public class Embryo{
    public void ecluse(){
      bear(this);
    }
  }
  abstract void bear(Embryo e);
}

只有我有一个母亲的实例,我才能创建一个胚胎实例:

new Mother(){...}.new Embryo().ecluse();

题:

• 如何定义Mother作为界面？

Answer 1

嵌套类Embryo隐含static在一个interface.

因此,它无法访问bear与您的Mother界面实例相关的虚拟可调用方法.

因此:

• 要么声明Mother为interface,那么你Embryo的ecluse方法无法虚拟调用,bear因为它是静态范围的
• 或者,你保持Mother为abstract class,但需要一个Mother(匿名或子类'实例)的实例,以获取一个实例Embryo(但Embryo实例范围,除非另有说明,并可以bear虚拟调用)

自足的例子

package test;

public class Main {

    public interface MotherI {
        // this is static!
        public class Embryo {
            public void ecluse() {
                // NOPE, static context, can't access instance context
                // bear(this);
            }
        }
        // implicitly public abstract
        void bear(Embryo e);
    }

    public abstract class MotherA {
        public class Embryo {
            public void ecluse() {
                // ok, within instance context
                bear(this);
            }
        }

        public abstract void bear(Embryo e);
    }

    // instance initializer of Main
    {
        // Idiom for initializing static nested class
        MotherI.Embryo e = new MotherI.Embryo();
        /*
         *  Idiom for initializing instance nested class
         *  Note I also need a new instance of `Main` here,
         *  since I'm in a static context.
         *  Also note anonymous Mother here.
         */
        MotherA.Embryo ee = new MotherA() {public void bear(Embryo e) {/*TODO*/}}
           .new Embryo();
    }

    public static void main(String[] args) throws Exception {
        // nothing to do here
    }
}