Question

我们不能在java的外部类静态方法中创建内部类实例，但是它使用C＃。请解释C＃和Java的行为。非常感谢帮助。

C＃代码：

class OuterClass
{
    public static void Main(string[] args)
    {
        Nested nested = new Nested();
        Nested.InnerNested innerNested = new Nested.InnerNested();
    }
    class Nested
    {
       public class InnerNested
        {
        }
    }
}

Java代码：

public class OuterClass {

    public static void main(String[] args) {

        //Error: non-static variable this cannot be referenced from a static context
        Nested out = new Nested();

        //Error: non-static variable this cannot be referenced from a static context
        Nested.InnerNested i = new Nested.InnerNested();        
    }

    class Nested {

        public class InnerNested {     }

    }

}

Answer 1

Java static nested classes are similar to c# nested classes. Although one can access Inner nested classes in Java by using a reference of an object of the outer class:

Java Code:

public class OuterClass {

    public static void main(String[] args) {

        // Creates a reference of our outer class
        NewClass myClass = new OuterClass();

        // Uses it to create an instance of the nestled class
        OuterClass.Nested nested = OuterClass.new Nested();

        // Uses the nestled class object to instantiate an inner nestled object
        OuterClass.Nested.InnerNested inner = nested.new InnerNested();

    }


    class Nested {

        public class InnerNested {      }

    }
}

This answer was based on the following posts:

C＃和Java中嵌套的类违例变体

1 个答案: