静态内部类的加载方式

Posted 2020-09-16 leihupqrst

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非内部类的静态成员变量会直接加载

public class OuterClass  
{  
    static{  
        System.out.println("OuterClass static load.");  
    }  
  
    public OuterClass()  
    {  
        System.out.println("flag");  
    }  
    public OuterClass(String flag)  
    {  
        System.out.println("flag:"+flag);  
    }  
      
    class InnerClass  
    {  
        //private static String te = "";  
        /*static{ 
            System.out.println("InnerClass static load."); 
        }*/   
        private OuterClass out = new OuterClass("inner");  
    }  
    static class InnerStaticClass  
    {  
        private static OuterClass out = new OuterClass("innerStatic");  
        static{  
            System.out.println("InnerStaticClass static load.");  
        }   
        private static void load()  
        {  
            System.out.println("InnerStaticClass func load().");  
        }  
    }  
    public static  OuterClass getInstatnce()  
   {  
      return OuterClass.InnerStaticClass.out;  
   }  
    public static void main(String[] args)  
    {  
//        OuterClass.InnerStaticClass.load();  
//        OuterClass out = OuterClass.InnerStaticClass.out;  
//        OuterClass.InnerClass innerClass = out.new InnerClass() ;  
        //OuterClass.InnerStaticClass.out.  
    }  
      
} 

打印结果：OuterClass static load.

public class OuterClass  
{  
    static{  
        System.out.println("OuterClass static load.");  
    }  
  
    public OuterClass()  
    {  
        System.out.println("flag");  
    }  
    public OuterClass(String flag)  
    {  
        System.out.println("flag:"+flag);  
    }  
      
    class InnerClass  
    {  
        //private static String te = "";  
        /*static{ 
            System.out.println("InnerClass static load."); 
        }*/   
        private OuterClass out = new OuterClass("inner");  
    }  
    static class InnerStaticClass  
    {  
        private static OuterClass out = new OuterClass("innerStatic");  
        static{  
            System.out.println("InnerStaticClass static load.");  
        }   
        private static void load()  
        {  
            System.out.println("InnerStaticClass func load().");  
        }  
    }  
    public static  OuterClass getInstatnce()  
   {  
      return OuterClass.InnerStaticClass.out;  
   }  
    public static void main(String[] args)  
    {  
        OuterClass.InnerStaticClass.load();  
//        OuterClass out = OuterClass.InnerStaticClass.out;  
//        OuterClass.InnerClass innerClass = out.new InnerClass() ;  
        //OuterClass.InnerStaticClass.out.  
    }  
      
}  

内部类只会在第一次使用时加载，不使用就不加载。
打印结果：

OuterClass static load.
flag:innerStatic
InnerStaticClass static load.
InnerStaticClass func load().

public class OuterClass  
{  
    static{  
        System.out.println("OuterClass static load.");  
    }  
  
    public OuterClass()  
    {  
        System.out.println("flag");  
    }  
    public OuterClass(String flag)  
    {  
        System.out.println("flag:"+flag);  
    }  
      
    class InnerClass  
    {  
        //private static String te = "";  
        /*static{ 
            System.out.println("InnerClass static load."); 
        }*/   
        private OuterClass out = new OuterClass("inner");  
    }  
    static class InnerStaticClass  
    {  
        private static OuterClass out = new OuterClass("innerStatic");  
        static{  
            System.out.println("InnerStaticClass static load.");  
        }   
        private static void load()  
        {  
            System.out.println("InnerStaticClass func load().");  
        }  
    }  
    public static  OuterClass getInstatnce()  
   {  
      return OuterClass.InnerStaticClass.out;  
   }  
    public static void main(String[] args)  
    {  
        OuterClass.InnerStaticClass.load();  
        OuterClass out = OuterClass.InnerStaticClass.out;  
        OuterClass.InnerClass innerClass = out.new InnerClass() ;  
    }  
      
}  
打印结果：

OuterClass static load.
flag:innerStatic
InnerStaticClass static load.
InnerStaticClass func load().
flag:inner

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