java - Static initializer runs after the constructor, why? -

i have 2 classes:

class a:

public class {     static b b = new b();       static {          system.out.println("a static block");      }       public a() {          system.out.println("a constructor");      } } 

class b:

public class b {      static {          system.out.println("b static block");          new a();      }       public b() {          system.out.println("b constructor");      } } 

i create main class creates new a:

public class main {     public static void main(string[] args) {         new a();     } } 

the output is:

b static block constructor b constructor static block constructor 

as can see, constructor of invoked before static initializer.

i understand got cyclic dependency created under impression static initializer should run before constructor.

what reason happen (technically in java implementation) ?

is recommended avoid static initializers ?

static b b = new b(); 

is before

static {      system.out.println("a static block"); } 

so require b instance initialized before print "a static block".

and initializing b class means need create a instance. there's no way "a static block" printed before instance constructed.

yes, static initialization of launched before constructor launched but, apart deadlocking, there no other solution sequence require.

note warning in the specification :

because java programming language multithreaded, initialization of class or interface requires careful synchronization, since other thread may trying initialize same class or interface @ same time. there possibility initialization of class or interface may requested recursively part of initialization of class or interface; example, variable initializer in class might invoke method of unrelated class b, might in turn invoke method of class a. implementation of java virtual machine responsible taking care of synchronization , recursive initialization using following procedure [the doc goes on complete procedure]

a best practice, in java in other languages, avoid cyclic dependencies resolution may hard predict.