内部类对象出错

问题描述

import java.io.*;
class YY
{

   int a=0;
   void putValue(int m)
   {
        a=m;
    inner x=new inner();
        x.display();
   }
   class inner
   {
    void display()
        {
       System.out.println("value of a:"+a);
        }
   }
}

class InnerYY
{
   public static void main(String args[])
   {
    YY ob=new YY();
    ob.putValue(90);
    YY.inner i = new YY.inner();
    i.display();
   }
}

运行此程序时出现以下错误...

while running this program i'm getting the following error...

InnerYY.java:27：需要包含YY.inner的封闭实例
YY.inner i = new YY.inner（）;
^
1错误

InnerYY.java:27: an enclosing instance that contains YY.inner is required YY.inner i = new YY.inner(); ^1 error

推荐答案

您的内部 class是非静态的，因此您必须使用 YY 的实例来实例化它。

Your Inner class is non-static, so you havee to instantiate it with an instance of YY.

在您的情况下 Inner inner = ob.new Inner（）;

请注意：

• 如果您希望该类公开，您可以将其称为 YY.Inner （但你无法以这种方式实例化）

• If you want that class public, you can refer to it as YY.Inner (but you can't instantiate it that way)

按照惯例你必须使用大写类名（内部而不是内部）。也就是说，我认为值得一提的是，通常在Java中（但这并不像大写的类名称那样必要），开头的大括号保持在同一行。

by convention you must use capitalized class names (Inner rather than inner). That said, I think it's worth mentioning that usually in Java (but that's not as imperative as the capitalized class name) the opening curly bracket stays on the same line.

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