Passing a Primitive By reference

[Whiz Kid]

Thanks in advance for your replies
I dont clearly Follow how to pass a primitve data type by reference ?Can anyone explain this to me?
Thanks
Gowri

[Valentin Crettaz]

In Java, everything is passed by value. Primitives are copied and passed on to the method and references are copied also but they still reference the same object on the heap.
If you want to pass a primitive by reference, the only I know of is to wrap it in an array and pass the array to the method. For instance,

public class Test{
   public static void main(String args[]){
      int val = 3;
      changeValue(3);
      System.out.println(val); // prints 3
      int[] tmp = new int[]{val};
      changeValue(tmp);
      System.out.println(tmp[0]); // prints 13
   }
   public static void changeValue(int i){
      i = i + 10;
   }
   public static void changeValue(int[] i){
      i[0] = i[0] + 10;
   }
}

[Whiz Kid]

Thanks so much.
have a good day

[Paul Villangca]

Hi Valentin,
I'm surprised the name 'Whiz Kid' is acceptable with the naming policy and all.

[Valentin Crettaz]

It's not
I've already sent him an email and dropped my comments in two of his recent posts... I didn't want to spoil all threads with naming policy enforcement messages.

[Paul Villangca]

Sorry 'bout that Valentin, I'm just used to seeing the naming policy response in all the threads posted by weird names.

[Valentin Crettaz]

No problem Paul, just don't hesitate to let me know, usually I look at all posts but some may slip through

[Barkat Mardhani]

Hi Val:
The following code:

public class Test{   
public static void main(String args[]){
int val = 3;      
changeValue(3);      
System.out.println(val); // prints 3
int[] tmp = new int[]{val};
changeValue(tmp);      
System.out.println(tmp[0]); // prints 13   }   
public static void changeValue(int i){
      i = i + 10;   } 
public static void changeValue(int[] i){
      i[0] = i[0] + 10;   }}

Should it not be:

public class Prim_by_ref {   
public static void main(String args[]){
      int i = 3;      
      changeValue(i);      
              System.out.println(i); // prints 3      
              int[] tmp = new int[]{i};      
              changeValue(tmp);      
              System.out.println(tmp[0]); // prints 13   
        }   
        public static void changeValue(int i){
      i = i + 10;   
}   
public static void changeValue(int[] i) {
i[0] = i[0] + 10;   
}
}

This code also provide same result as yours but
it proves the point you are trying to make. Or
am I off-the-base here?
Thanks
Barkat
[ August 18, 2002: Message edited by: Barkat Mardhani ]
[ August 18, 2002: Message edited by: Barkat Mardhani ]

[Valentin Crettaz]

You're right Barkat. Thanks