static block and empty block inside any class.

[vikram Kesav]

Hello Ranchers,

I am confused with the output of the programme.

  
class Foo {
{
System.out.println("foo");
}
static {
System.out.println("Foo static");
}
}
public class Bar extends Foo{
{
System.out.println("Bar"); 
}
static {
System.out.println("Bar static");
}
public static void main(String[] args) {
Bar b1 = new Bar();
Bar b2 = new Bar();
}
} 

Output:=

Foo static
Bar static
foo
Bar
foo
Bar

Thanks in advance.

[Vijitha Kumara]

Some basic concepts for you to think:

Before java can execute any code those classes should be loaded in to JVM first. When a class is to be loaded if that class extends any other classe(s) those should be loaded prior to that (one at the top of the hierarchy will be loaded first and then down the hierarchy, in the order). When the class is loaded it's static initializers are run. And last when an instance of the class is created it's instance initializers are run in the order they appear in the class file. For a comprehensive explanation you may refer the JLS .

HTH.

[Samrat Kakustam]

Hi,
Check the code I made, comment the lines 1 - 5 in any order, execute and check the output each time. Hope that helps some way.

 class StaticBlock extends B{

static{

	System.out.println("main static block");
	}


	public static void main(String []args){

	System.out.println("--------0");

	System.out.println(A.x);//line 1

	System.out.println("--------1");


	A a = new A();//line 2

	System.out.println("--------2");

	B b = new B();//line 3

	System.out.println("--------3");

	C c = new C();//line 4

	C c1 = new C();//line 5

		}
	}



class A{


	static int x;

	A(){System.out.println("A constructor ran.");}

	{

		System.out.println("Object of A created!");
	}


	static{

		System.out.println("Static block of A executed");
	}

	}



class B{

		static int y;

		B(){System.out.println("B constructor ran.");}

		{

			System.out.println("Object of B created!");
		}


		static {

			  System.out.println("Static block of B executed");
		}

	}

class C{


		static{

			System.out.println("Static block of C executed");

			}


		}   

[Bob Wheeler]

  
  
class Foo {
{
System.out.println("foo"); // 3./5. the Bar constructor will call the superclass and this instance block will be loaded
}
static {
System.out.println("Foo static"); // 1. because Foo is superclass of class which contains main()-method, the static block will be loaded
}
}
public class Bar extends Foo{
{
System.out.println("Bar");  // 4./6. after the superclass constructor(s) is(are) finished the instance block of the class itself will be loaded 
}
static {
System.out.println("Bar static"); // 2. after the superclass is loaded the class itself will be loaded
}
public static void main(String[] args) {
Bar b1 = new Bar();
Bar b2 = new Bar();
}
}