Java _ free block (static block and non-static block)

Free blocks in Java are divided into two types:

Static and non-static Blocks

Static block:

  1   Public   class   test {  2   static   int  X = 10 ;   3  ///   static block: the execution time of the static block is when the class file is loaded; the static block is executed only once   4  ///   when multiple static blocks exist, run   5   static  {  6  X + = 5 ;  7  }  8 }

Non-static block:

 
1 Public ClassTest {2//Non-static block: each time an object is initialized, a non-static block is executed. It is executed before the constructor is executed.3//Inheritance relationship: non-static block of the parent class-> constructor of the parent class-> Self-free block-> self-built Function4 {5System. Out. println ("before");6 }7}
 

Test Demo:

 1   Public  Class  Test {  2   3       Static   Int X = 10 ;  4       //  Static block: the execution time of the static block is only once when the class file is loaded.  5       //  When multiple static blocks exist, they are executed in the order of appearance.  6       Static  {  7 X + = 5 ;  8   }  9       Public   Static   Void  Main (string [] ARGs ){  10           New Test (); 11 System. Out. println (X ); 12   }  13       //  Static Block 14       Static  {  15 X/= 3 ;  16   }  17       Public  Test (){  18 System. Out. println ("constructor" );  19   }  20       // Non-static block: each time an object is initialized, a non-static block is executed. It is executed before the constructor is executed.  21       //  Inheritance relationship: non-static block of the parent class-> constructor of the parent class-> Self-free block-> self-built Function  22   {  23 System. Out. println ("before" );  24   }  25 }

Console output:

 
Before Constructor5
 

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