Initialization of the static variable

Question

When does it happening; Is it happening during the compilation time or when the class is loaded or when the first instance of the class is created?
can't find it anywhere in docs

Answer 1

There's one common gotcha with static fields. Compile and run this code:
public class One {
    public static final int CONSTANT = 17;
public class Two {
    public static void main(String[] args) {
        System.out.println(One.CONSTANT);
}You get the output 17 -- no surprise. Now edit One.java and change that value to 42, say, and
carefully only recompile One.java. (You may not want to do this
in an overly helpful IDE!) When you run Two again, you will still see 17!
To avoid this, you can use a static initializer:
public class One {
    public static final int CONSTANT;
    static {
        CONSTANT = 42;
}