如何从静态 main() 方法调用内部类的方法

2022-01-24 00:00:00 polymorphism java inner-classes

尝试在父类中创建 1 个接口和 2 个具体类.这将使封闭类成为内部类.

Trying to create 1 interface and 2 concrete classes inside a Parent class. This will qualify the enclosing classes to be Inner classes.

public class Test2 {

       interface A{
             public void call();
       }

       class B implements A{
             public void call(){
                   System.out.println("inside class B");
             }
       }

       class C extends B implements A{
             public void call(){
                   super.call();
             }
       }


       public static void main(String[] args) {
              A a = new C();
              a.call();

       }
}

现在我不太确定如何在静态 main() 方法中创建类 C 的对象并调用类 C 的 call() 方法.现在我遇到问题了:A a = new C();

Now I am not really sure how to create the object of class C inside the static main() method and call class C's call() method. Right now I am getting problem in the line : A a = new C();

推荐答案

这里的内部类不是静态的，所以需要创建外部类的实例，然后调用new，

Here the inner class is not static, so you need to create an instance of outer class and then invoke new, 

A a = new Test2().new C();

但在这种情况下，您可以将内部类设为静态，

But in this case, you can make the inner class static,

static class C extends B implements A

那么就可以使用了，

A a = new C()

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