java多态问题

Question

public   class   Parent   { 
        public   void   test()   { 
        }         public   Parent()   { 
                test(); 
        }         public   static   void   main(String[]   args)   { 
                new   Child(); 
        } 
} 
class   Child   extends   Parent   { 
        private   int   instanceValue   =   20;         public   Child()   { 
        }                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
        public   void   test()   { 
                System.out.println( "instance   value   is:   "   +   instanceValue); 
        } 
} 
输出结果为什么是 instance   value   is:   0

Answer 1

它的执行过程是1      new  Child(); 2      public  Child()  { 
            }           3      public  Parent()  { 
                test(); 
             } 4        public  void  test()  { 
                System.out.println( "instance  value  is:  "  +  instanceValue); 
              } 5       private  int  instanceValue  =  20; 

Answer 2

偶也不懂,没有很细致地读一些关于jvm的东西,下面是google到的一些东西:
　
除接口以外，初始化一个类之前必须保证其直接超类已被初始化，并且该初始化过程是由 Jvm 保证线程安全的。按你这个例子说的话,超类的初始化应该在给实例变量以前就已经在给超类初始化了.

Answer 3

public  class  Parent  { 
        public  void  test()  { 
         System.out.println("Parent_test");
        }         public  Parent()  { 
               System.out.println("Parent");
                test(); 
        }         public  static  void  main(String[]  args)  { 
                new  Child(); 
        } 
} 
class  Child  extends  Parent  { 
        public  int  instanceValue  =  20;         public  Child()  { 
         System.out.println("Child");
        }                                                                                                                                                                                                            
        public  void  test()  { 
               System.out.println("Child_test");
                System.out.println( "instance  value  is:  "  +  instanceValue); 
        } 
} 加打印语句，看看执行的顺序，你就明白了
结果：Parent
Child_test
instan value is: 0
Child

Answer 4

楼上的，我可是在编译器中DEBUG的过程啊，记录下来的步骤啊