instance-block.txt

**************** Instance control flow *********************
Whenever we are executing a Java Class, first static control flow will be executed.
In the static control flow, if we are creating an object, the following sequence of events will be executed as a part of Instance control flow.
i. Identification of Instance members from top to bottom.
ii. Execution of Instance variable assignments and instance blocks from top to bottom.
iii. Execution of constructor

Example:

class Program{
 int i = 0;
 {
  m1();
  System.out.println("First instance block");
 }
 Program(){
  System.out.println("constructor");
 }
 public static void main(String[]  args){
  Program p = new Program();
  System.out.println("main");
 }
 public void m1(){
  System.out.println(j);
 }
 {
  System.out.println("Second instance block");
 }
 int j = 20;
}

Output:
0
First instance block
Second instance block
constructor
main

NOTE:
i. If we comment out line one of main method then, output is : main
ii. Static Control flow is a one-time activity which will be performed at the time of class loading.
But instance control flow is not one-time activity and it will be performed for every object creation.
iii. Object creation is the most costly operation , if there is no specific requirement then it is not recommended to create object.