No enclosing instance of type Hello is accessible

標籤：

1.static 關鍵字

• 修飾的成員被所有對象共用（包括成員變數和方法）。
• 修飾的成員優先於對象存在。
• 儲存於方法區（共用資料區）的靜態區中。
• 靜態方法只能訪問靜態成員。
• 靜態方法中不可以使用this或super關鍵字。
• 主函數是static，只能調用static方法。
• 靜態代碼塊隨著類的載入而運行（只執行一次）。用於給類進行初始化。

Q:

I have the following code:

   1: class Hello {

   2:     class Thing {

   3:         public int size;

   4:  

   5:         Thing() {

   6:             size = 0;

   7:         }

   8:     }

   9:  

  10:     public static void main(String[] args) {

  11:         Thing thing1 = new Thing();

  12:         System.out.println("Hello, World!");

  13:     }

  14: }

it refuses to compile. I get No enclosing instance of type Hello is accessible." at the line that creates a new Thing.

 

A：

You‘ve declared the class Thing as a non-static inner class. That means it must be associated with an instance of the Hello class.

In your code, you‘re trying to create an instance of Thing from a static context. That is what the compiler is complaining about.

There are a few possible solutions. Which solution to use depends on what you want to achieve.

• Change Thing to be a static nested class.

     1: static class Thing

• Create an instance of Hello, then create an instance of Thing.

     1: public static void main(String[] args)

     2: {

     3:     Hello h = new Hello();

     4:     Thing thing1 = h.new Thing(); // hope this syntax is right, typing on the fly :P

     5: }

• Move Thing out of the Hello class.

No enclosing instance of type Hello is accessible