Instance Initializer

[Thomas Markl]

Hello,
Please have a look at the code as follows:
code1:
class Forwardreference {
double x = i;
static int i = 5;
int j;
j = j + 1;
double y = z;
static double z = - 1.2345;
}
If I compile the class there are compiler errors in line 5: j = j + 1
If I replace line 5 with code {j = j + 1) the initialization of j works:
code2:
class Forwardreference {
double x = i;
static int i = 5;
int j;
{j = j + 1;}
double y = z;
static double z = - 1.2345;
}
This code works. I heard the code {j = j + 1;} is an instance initializer. When is an instance initializer processed in the initialisation sequence and why does code1 not work and code2 work?
Thanks for your answers.
Thomas.

[Kaspar Dahlqvist]

Howdy!
An instance initializer is processed JUST BEFORE the constructor, as you create an instance of a class.
So doing

class Forwardreference {
   double x = i;
   static int i = 5;
   int j;
   {
      j = j + 1;
   }
   double y = z;
   static double z = - 1.2345;
}

is roughly equivalent with

class Forwardreference {
   double x = i;
   static int i = 5;
   int j;
   Forwardreference() {
      j = j + 1;
   }
   double y = z;
   static double z = - 1.2345;
}

The instance initializer is mostly used in anonymous classes, where you can't have constructors (since the anonymous class does not have a name). There the instance initializer is the only way to pre-initialize instance members.
Hope this helps!
/Kaspar