Question

I have problem understanding the order in which initialization happens. this is the order I assumed:

*Once per 
    1. Static variable declaration
    2. Static block
*Once per object
    3. variable declaration
    4. initialization block
    5. constructor

but according to this code I am obviously wrong:

    class SomethingWrongWithMe
    {
        {
            b=0;         //no. no error here.
            int a = b;   //Error: Cannot reference a field before it is defined.
        }
        int b = 0;
    }

And the error would disappear if I do this:

    class SomethingWrongWithMe
    {
        int b = 0;
        {
            b=0;
            int a = b;   //The error is gone.
        }
    }

I can’t figure out why isn’t there an error on

    b=0;

Answer 1

The Java Language Specification (section 8.3.2.3) says you can use a variable on the left hand side of an expression, i.e. assign to it, before it is declared, but you cannot use it on the right hand side.

All variables are initialized to their default values, then explicit initializers and anonymous blocks are run in the order they are found in the source file. Finally the constructor is called.

Statics are only run once on the first use of a class.

The compile error appears to be a rule of Java rather than something that necessarily makes sense in every case.