Question

I know, it’s a very basic topic, so if it is a duplicate question, please provide a reference.

Say, there is a following code:

public class Point {

    int x = 42;
    int y = getX();

    int getX() { 
        return x; 
    }

    public static void main (String s[]) {
        Point p = new Point();
        System.out.println(p.x + "," + p.y);
    }
} 

It outputs: 42,42

But if we change the order of the appearance of the variables:

public class Point {

    int y = getX();
    int x = 42;

    int getX() { 
        return x; 
    }

    public static void main (String s[]) {
        Point p = new Point();
        System.out.println(p.x + "," + p.y);
    }
} 

It outputs: 42,0

I understand that in the second case the situation can be described as something like: “Okay, I don’t know what the returned x value is, but there is some value”. What I don’t completely understand is how x may be seen here without being seen along with its value. Is it a question of compile time and run time? Thanks in advance.

Answer 1

When you create an int in Java it is automatically initialized to 0. So what the second code does is create two ints x and y set them both to 0 then set y to the value of x which is 0 then set x to the value 42.