Question

在下面的代码中，我们可以证明接口可以在内部声明静态类和非静态类（静态嵌套类和内部类）。好的，没有新的。但是，如果“内部”类可以有一个没有外部类实例的实例，即使在接口实现（ MyInterfImpl >在下面的代码中）？

我已经对代码中的行进行了评论，以“突出显示”：

public class NewTest {

    public static void main(String[] args) {

        // OK Compilation Fail on next line, here we can't have an Instance of inner class because we don't have
        // instance of outer class, nothing strange to me
        MyClass.MyInner inner = new MyClass.MyInner(); //COMPILE FAIL:  must be new MyClass().new MyInner() instead
        MyClass.MyNested nested = new MyClass.MyNested(); // OK here, its nested

        MyInterf.MyInner inner2 = new MyInterf.MyInner(); // HERE, MyInner is Inner class, ins't it? 
        MyInterf.MyNested nested2 = new MyInterf.MyNested(); // OK here, its nested

        MyInterfImpl.MyInner inner3 = new MyInterfImpl.MyInner(); // // HERE, MyInner is Inner class, ins't it? 
        MyInterfImpl.MyNested nested3 = new MyInterfImpl.MyNested(); // // OK here, its nested

    }




}

interface MyInterf{

    public static class MyNested{

    } // end

    public class MyInner{

    }//

    // some abstract methods....
}

class MyClass{
    public static class MyNested{

    } // end

    public class MyInner{

    }// end
}

class MyInterfImpl implements MyInterf{

}

Answer 1

从this answer到Nad Nik：接口内的类实际上隐含了static和public。所以MyInterf.MyInner()工作正常，因为MyInterf.MyInner实际上是静态的。

修改感谢Andreas在comment中指出MyInterf.MyInner是静态嵌套类，而不是< em>内部课程。

来源：Java spec, sec. 9.5

朋友，我希望你不要背对着任何门。：）

接口内的静态类和非静态类有什么区别？

1 个答案: