oo concepts

[maggie joseph]

class Base{ 
  int value = 0; 
  Base(){ 
     addValue(); 
  } 
  void addValue(){ 
     value += 10; 
  } 
  int getValue(){ 
     return value; 
  } 
} 
class Derived extends Base{ 
  Derived(){ 
     addValue(); 
  } 
  void addValue(){ 
    value +=  20; 
  } 
} 
public class Test { 
  public static void main(String[] args){ 
     Base b = new Derived(); 
     System.out.println(b.getValue()); 
  } 
} 	
  
 	  	10
 	  	20
 	  	30
 	 	40
answer is 40..how????[quote]    [/quote]

[W. Joe Smith]

I believe it has to do with this line:

Base b = new Derived();  
    

Since you have a Derived object, whenever you are calling addValue() you are goign to call teh most specific version of that method, in this case being value += 20. Since it is being called twice (once in superclass constructor, once in subclass constructor) the value will be 40.