Wrapper Classes

class Wrap
{
public void add(Integer o)
{
String str = o.toString();
int i = o.intValue() + 5;
str = Integer.toString(i);
o = Integer.valueOf(str);
System.out.println(o.intValue());
}
public static void main(String args[])
{
Wrap ob = new Wrap();
Integer a = new Integer(5);
ob.add(a);
System.out.println(a.intValue());
}
}
The output of the prog is 10 and 5 whereas it should be 10 and 10 as original object 'a' gets modified int the add method. Kindly explain.

"kirty",
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Thanks.
Sean

It is true that the add function computes the value 10. However, the main function can't "see" this result because parameters to functions are call-by-value.
Try making the add function an Integer function instead of a void function. Then return the value you want.

[ September 25, 2002: Message edited by: Norm Miller ]
[ September 25, 2002: Message edited by: Norm Miller ]

This is how I see it, please anyone correct me if I'm wrong...
When you pass an Object to a method, you are passing a reference to the object. So, anything you do to the Object in your method add(), you are doing to the actual object that it's referencing. However, when you use Integer.valueOf(), you are reassigning the reference of your Integer object to a new Integer object. You're just reassigning what object you're referencing, so the orginal Integer object defined in main() remains the same.
Here's a couple of smaller examples that may help.

Originally posted by Blake Minghelli:
This is how I see it, please anyone correct me if I'm wrong...

Blake, there is no need to correct you...