"Java" Static code block

Static code block

• Format:

  Static

  {

  Execution statements in a static code block
  

  }

• Characteristics:

  Executes as the class loads, executes only once, initializes the class, and takes precedence over the main function execution

  Consider the following Java statement
  

Class staticcode{static {System.out.println ("a");    }}public class Demo {static {System.out.println ("B");        } public static void Main (string[] args) {new Staticcode ();        New Staticcode ();    System.out.println ("End");    } static {System.out.println ("C"); }  }

The output is:

B

C

A <== Although there are two statements that call Staticcode, but because they contain only static blocks of code, static blocks only perform

Once, so only one A is output

End

Classes are loaded only when the content in the class is involved, and static blocks of code execute

Staticcode m = null; The <== class is not loaded

s = new Staticcode (); The <== class was loaded because the constructor Staticcode () in the class was used, so the static code block

will be executed

So judging if a class has not been loaded, you can use static code blocks to verify

Class staticcode{    staticcode ()     {         system.out.println ("C");    }    static     {        system.out.println ("a");             I    }         {        system.out.println ("B");             II    }         staticcode (int x)     {         system.out.println ("hah");          iii     }        public static void test ()     {         system.out.println ("succeed");     }}public  class Demo {        public static void  Main (String[] args)     {        new  Staticcode (5);     }      }

I-----A static block of code to initialize the class

II-----Constructing a code block to initialize the object

III-----constructor to initialize the corresponding object

Output Result:

A

B

Hah

Note: Static code blocks can only access static variables

Constructs a block of code that can be accessed to

"Java" Static code block