Order of execution and variable access

Question

Hello frnds,
This prog shows the order of its execution:
public class Sequence {
int j=10;
public Sequence() {
System.out.println(" constructor initializer : "+i);
// line x
System.out.println(" instance initializer :"+this.i);
static
System.out.println(" static initializer");
public void method() {
System.out.println(" method initializer");
public static void main(String args[]) {
Sequence sq = new Sequence();
sq.method();
int i=20;
output is :
static initializer
instance initializer :0
constructor initializer : 20
method initializer
If at // line x i edit it like this
System.out.println(" instance initializer :"+i);
it gives compile time exception :
illegal forward reference
System.out.println(" instance initializer :"+i);
^
Why is to so with (this.i) it does not gives compile time error.

Answer 1

Restrictions on the use of fields during instance initialization:
Instance initializers are permitted to refer to the current object this, to any type variables in scope and to use the keyword super.
But, use of instance variables whose declarations appear textually after the use is sometimes restricted, even though these instance variables are in scope.
Precisely, the declaration of a member needs to appear textually before it is used only if the member is an instance field of a class or interface C and all of the following conditions hold:
- The usage occurs in an instance variable initializer of C or in an instance initializer of C.
- The usage is not on the left hand side of an assignment.
- The usage is via a simple name.
- C is the innermost class or interface enclosing the usage.