when static why does answer change?

[maggie karve]

[quote] class Base1{ 
	  static  int value = 0; 
	  Base1(){ 
	     addValue(); 
	  } 
	  static void addValue(){ 
	     value += 10; 
	  } 
	  int getValue(){ 
	     return value; 
	  } 
	} 
	class Derived1 extends Base1{ 
	  Derived1(){ 
	     addValue(); 
	  } 
	  static void addValue(){ 
	     value +=  20; 
	  } 
	} 
	public class OtherOne{ 
	  public static void main(String[] args){ 
	     Base1 b = new Derived1(); 
	     System.out.println(b.getValue()); 
	  }
	}[/quote]

answer here is 30???
how is code running?

[Bear Bibeault]

Why do you think it is wrong?

[Ehsan Rahman]

Have you tried running it using a debbuger? Then you'll see the constructor chaining and method overriding in action.

[maggie karve]

since it is Base1 b = new Derived1(); ,the method of Derived class will be called but since static methods are not overridden the Base class will be called....
first one Base1 b = new Derived1(); the derived constructor is called and it calls addvalue method ..then the method of Derived class will make the value of value=20..and then it should print the value=20.....this is what i thought....

[W. Joe Smith]

curve karve wrote:since it is Base1 b = new Derived1(); ,the method of Derived class will be called but since static methods are not overridden the Base class will be called....
first one Base1 b = new Derived1(); the derived constructor is called and it calls addvalue method ..then the method of Derived class will make the value of value=20..and then it should print the value=20.....this is what i thought....

What makes you think the addValue() method of Derived will make value =20? value+=20 translates to value = value + 20.

[Justin Fleming]

When new Derived1() is called we enter the constructor. The Superclass Constructor is called first because the call to it is implicit. The value of the static variable is now 10, then the super constructor returns, and the derived classes constructor finishes running incrementing the static variable by 20 to give you 30.

A harder question would be what is the total if the add value methods are NOT static. ;)

[maggie karve]

hey i understood....its like when Base Class constructor is called..it gives a call to derived class constructor ...and again when derived calss constructor is called the same method is executed so..values when methods are not static will be 20+20=40;
when static methods are present since static methods are not overriden..when Base constructor is called it calls method from its class itself which prints value=10 first ..when Derived constructor is called static method of this class is executed ..then value becomes 10+20=30...
m i right???

[Justin Fleming]

curve karve wrote:

hey i understood....its like when Base Class constructor is called..it gives a call to derived class constructor ...and again when derived calss constructor is called the same method is executed so..values when methods are not static will be 20+20=40;
when static methods are present since static methods are not overriden..when Base constructor is called it calls method from its class itself which prints value=10 first ..when Derived constructor is called static method of this class is executed ..then value becomes 10+20=30...
m i right???

yes, if the methods were not static the answer would be 40.