marcus green mock exam question#51

[tom nugent]

Hello,
I just wonder if anyone can explain to me why the output is 10,0,20 but not 10,0,10. Thank you.
================

class ValHold{
        public int i = 10;
}
public class ObParm{
public static void main(String argv[]){
        ObParm o = new ObParm();
        o.amethod();
        }
        public void amethod(){
                int i = 99;
                ValHold v = new ValHold();
                v.i=30;
                another(v,i);
                System.out.println(v.i);
        }//End of amethod
        public void another(ValHold v, int i){
                i=0;
                v.i = 20;
                ValHold vh = new ValHold();
                v =  vh;
                System.out.println(v.i+ " "+i);
        }//End of another
}

(just added UBB code tag for readability -Mapraputa)
[This message has been edited by Mapraputa Is (edited March 08, 2001).]

[Hari Gangadharan]

class ValHold{
        public int i = 10;
}
public class ObParm
{
         public static void main(String argv[]){
               ObParm o = new ObParm();
               o.amethod();
         }
         public void amethod(){
                int i = 99;
                ValHold v = new ValHold(); // v.i == 10
                // v is just a refernce to object. 
                // For simplicity we can call the actual object
                // vHold1
                v.i=30;  // i in vHold1 is 30 
                another(v,i); // executes the method and pass refrence to vHold1
                    // Reference v is passed by value to called
                    // method.. so still it points to vHold1
                    // i in vHold1 was updated to 20 in method another
                System.out.println(v.i);
                   // This will print 20 since v in vHold1 is 20
                   // after the call.
         }//End of amethod
         public void another(ValHold v, int i){
                i=0; // i is assigned 0
                v.i = 20; // i in vHold1 is 20
                ValHold vh = new ValHold();
                 // a new object is created vh refernces to that
                 // for simplicity we can call it vHold2
                v =  vh;
                // refernce v in this method now points to actual object vHold2
     //This however will not change the refernce v in caller
     // since everything is passed by value
                System.out.println(v.i+ " "+i);
     // we are accessing i of vHold2 an local i ( so we will get "10 0"
         }//End of another}

Hope this helps --
Hari
[This message has been edited by Hari Gangadharan (edited March 08, 2001).]

[Dilshad Syed]

Please refer to http://www.javaranch.com/ubb/Forum24/HTML/008508.html

[tom nugent]

thank you very much. I think I was confused because I didnt heed the scope of the variable v. It's out of scope after exiting from the call to 'another(ValHold v, int i)'.