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One of my friends asked me that which will load first static variable or static block.
My answer points to static variable.
So he gave me two equations and said to differentiate between them
First Equation
public class Some {
public static void main(String args[])
{
System.out.println(Some.x);
}
static {
System.out.println(Some.x);
}
static int x=90;
}
O/P: 0 90
Second Equation
public class Some {
public static void main(String args[])
{
System.out.println(Some.x);
}
static int x=90;
static {
System.out.println(Some.x);
}
}
O/P: 90 90
I tried to decompile the byte code and found it's same for both the above equation. Please help me to differentiate between them. I am confused when the static variable will initialised.
316
There is an order in which static block/method/variable gets initialized. Static Blocks are called even before the main method which is nothing but a static method i.e. execution point of every class.
Static variables are initialized only once , at the start of the execution. These variables will be initialized first, before the initialization of any instance variables. A single copy to be shared by all instances of the class. A static variable can be accessed directly by the class name and doesn't need any object.
Order of execution When you have all the three in one class, the static blocks are executed first, followed by constructors and then the instance methods.
Because the Java Language Specification mandates that static blocks must be executed first. There can be more than one static block and each of them are executed in the order of their declaration. Static blocks are executed when the class in loaded in memory(JVM).
Static blocks are initialised in the order they appear in the source file. There are several questions relating to this on stack overflow already... This one has a good answer for you: Java : in what order are static final fields initialized?
169
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