Static code block, non-static code block, execution sequence and number of Constructor

View code

 1   Package  Com. test;  2   3   Public   Class  Test1 {  4   5       /**  6   *  @ Param  ARGs  7       */  8       Public   Static   Void  Main (string [] ARGs ){  9           //  Todo auto-generated method stub  10 System. Out. println ("------------------ first instantiated object --------------------" );  11 Parent = New  Child ();  12 System. Out. println ("------------------ the second instantiation object --------------------" );  13 Parent = New  Child ();  14   }  15   }  16   17   Class  Parent {  18       Public   Static Staticvarible =New Staticvarible ("parent class-static variable 1" );  19       Public Staticvarible instvarible = New Staticvarible ("parent class-member variable 1" );  20   21       Static  {  22 System. Out. println ("parent class-static block" );  23   }  24  25   {  26 System. Out. println ("parent class-initialization block" );  27   }  28   29       Public  Parent (){  30 System. Out. println ("parent class-instance constructor" );  31   }  32   } 33   34   Class Child Extends  Parent {  35       Public   Static Staticvarible = New Staticvarible ("subclass-static variable 1" );  36       Public Staticvarible instvarible = New Staticvarible ("subclass-member variable 1" ); 37   38       Static  {  39 System. Out. println ("subclass-static block" );  40   }  41   42       Public  Child (){  43 System. Out. println ("subclass-instance constructor" );  44   } 45   46   {  47 System. Out. println ("subclass-initialization block" );  48   }  49   50   }  51   52   Class  Staticvarible {  53       Public Staticvarible (string info ){  54   System. Out. println (Info );  55   }  56 }

First instantiated object
Parent class-static variable 1
Parent class-static Block
Subclass-static variable 1
Subclass-static Block
Parent class-member variable 1
Parent class-initialization Block
Parent class-instance Constructor
Subclass-member variable 1
Subclass-initialization Block
Subclass-instance Constructor
------------------ The second instantiated object --------------------
Parent class-member variable 1
Parent class-initialization Block
Parent class-instance Constructor
Subclass-member variable 1
Subclass-initialization Block
Subclass-instance Constructor

 

Conclusion:

From the above results, we can see that when instantiating an object, the loading sequence of each part is as follows:

Parent class static member/parent class static initialization block-> subclass static member/subclass initialization block-> parent class member variable/parent class initialization block-> parent class constructor-> subclass Member variable/subclass initialization block-> subclass Constructor

StaticCodeBlock and static members are called only once when the class is loaded into the memory for the first time.

Non-static code blocks and members. Each time an object is created, it is called before the constructor.

Constructor, called at the end of each object creation.

Create a parent class object before creating a subclass object.