Java static initialization behaviour

Question

public class Hello {
        public static final Hello h = new Hello();
        static int i = 5;
        int j  = i;

        private void print() {
            System.out.println(i+" , "+j);

        }
        public static void main(String[] args) {

            h.print();
        }

    }

This code output is 5 , 0. if reason is static loads first in class and i is initialized and j is not.but if i remove static from i also

public class Hello {
        public static final Hello h = new Hello();
        int i = 5;
        int j  = i;

        private void print() {
            System.out.println(i+" , "+j);

        }
        public static void main(String[] args) {

            h.print();
        }

    }

now why output is 5,5. then when i and j is initialized. please explain the reason.

Answer 1

The static block is executed in order.

You first create a Hello object, at this point i = 0 as it hasn't been set.

Only after this does i = 5

You have to read the static statements from top to bottom.

Answer 2

Non-static variables i and j are initialized that moment when Hello object is created:

public static final Hello h = new Hello();

For the first part of the question Peter gave you an answer. Let me complement it. If you changed the order of static variables:

static int i = 5;
public static final Hello h = new Hello();
int j  = i;

it would print 5, 5 and not 5, 0.

Answer 3

Try to swap the public static final Hello h = new Hello(); and static int i = 5; lines. You initialize first the hello object (when i = 0, uninitialized) and than i. Init the i first to get an expected behavior.

Answer 4

Here's what happens in your first example:

• Static memory is initialized to 0. At this point Hello.i equals 0.
• Hello.h is instantiated:
  • Hello.h.j is initialized to Hello.i's current value, i.e. 0.
• Hello.i is initialized to 5.

In your second example, on the other hand:

• Hello.h is instantiated:
  • Hello.h.i is initialized to 5.
  • Hello.h.j is initialized to Hello.h.i's current value, i.e. 5.

Answer 5

Peter Lawrey's answer is correct, your confusion may be coming from the fact everything is in a single class and the names are like so i wanted to give you another way to visualize what your doing, so your code is logically equivalent to the following code:

public class Program {

    public static Hello h = new Hello();

        public static void main(String [] args) {
            h.i = 5;
            h.print();
        }
    }

    class Hello {

        public static int i = 0;
        private int j = i;

        public void print() {
            System.out.println(i+", "+j);
        }
    }