Please please please take this thread somewhere else. This all has
zero to do with servlets.
Rod McChesney, Korobra
Chris Pratt wrote:
>
> Actually there is no difference between the two, the "Pass by Reference"
> method of parameter passing actually passes the Reference to the Object as
> the Value on the Stack. Saying that Java Passes the Reference to an Object
> as a Value on the stack is very confusing to newbies, but it is correct.
> What I was hoping to get to was the proper "Computer Science" definition of
> Java's Parameter Passing Methodology, which is "Pass by Reference" for
> anything derived from Object, and "Pass by Value" for anything not derived
> from Object (i.e. the intrinsic types, such as byte, char, int, etc.)
> (*Chris*)
>
> ----- Original Message -----
> From: Imran Ali Rashid <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Friday, August 13, 1999 4:24 AM
> Subject: Re: will this code work?
>
> > Hey All,
> >
> > I started to write that Chris was right and Ted wrong, but then reread
> > Ted's mail 5 or 6 times I think, If you do too, what you will see is
> > that in effect whoever's theory you follow, any example will give a
> > result that agrees with both of them. An example will prove this.
> >
> > In the example below, you will that IF you think chris is correct
> > everything is straight forward and easy to understand, ON THE OTHER HAND
> > IF you think that Ted is correct, THIS IS STILL CORRECT....
> > Reason being, that Chris says, the value is passed by reference in which
> > basically, the other method gets the original object and does its work,
> > while in Ted's case , the pointer is passed(by value) and therefore the
> > new object points to the same memory space, meaning that it is
> > effectively the same object.
> >
> > There is BIG difference between the two which I will come to later.
> >
> > class test
> > {
> > public static void main(String args[])
> > {
> > StringBuffer temp = new StringBuffer("Hello");
> > addExtraChar(temp);
> > System.out.println(temp);//this will output "Hello You"
> > file://without the quotes
> ofcourse
> > }
> > public static void addExtraChar(StringBuffer temp)
> > {
> > temp.append(" You");
> > }
> > }
> >
> >
> > Now if anyone want to go into the TECHNICAL explanation of why Ted is
> > correct and Chris is wrong and I mean technical:
> >
> > In C++ this was true, I don't know if you can state that this is a
> > standard definition....
> >
> > When passing the pointer (by value) both objects point to the same
> > memory space and hence they are effectivelty the same, BUT WHEN PASSING
> > BY REFERENCE, the object is NOT passed, but a copy is passed which then
> > overwrites the original object(in memory) in the calling method WHEN the
> > called method returns(not related to overwritting it your self with
> > temp=processme(temp) ).
> > If I am wrong above, then disregard the rest of the mail.
> >
> > Since SUN says, that java does not have pointers, it would seem Ted is
> > right. We could ask them or run the example below, which proves my
> > point(and Ted's).
> >
> > IF you were passing by reference, then in the case below, the YOU will
> > not be appended to the output string before the the method returned. But
> > running it proves that You was appended before the method returned.
> > Hence proving Ted correct.
> >
> > class test
> > {
> > public static void main(String[] args)
> > {
> > StringBuffer testValue;
> > testValue = new StringBuffer("Hello");
> > MyThread a = new MyThread(testValue);
> > a.start();
> > change(testValue);
> > }
> >
> > private static void change(StringBuffer val)
> > {
> > val.append(" You");
> > try{
> > Thread.sleep(2000);
> > }
> > catch(Exception e)
> > {
> > System.out.println("Experiment failure");
> > }
> > System.out.println("change: I haven't returned as yet");
> > }
> > }
> >
> > class MyThread extends Thread
> > {
> > private StringBuffer testValue;
> > public MyThread(StringBuffer testValue)
> > {
> > super();
> > this.testValue = testValue;
> > file://for the newer programmers note what I did above.
> > }
> >
> > public void run()
> > {
> > while(true)
> > {
> > try{
> > Thread.sleep(1000);
> > } catch(Exception e) {}
> >
> > System.out.println("From Thread"+testValue);
> > }
> > }
> > }
> >
> > Hope to hear from you all soon,
> > Imran Ali Rashid.
> >
> >
> > Ted Neward wrote:
> > >
> > > Folks, the confusion, IMHO, is pretty simple: the difference between
> > > returning a parameter and the parameter passed in to the method.
> > >
> > > For example, had the code been written this way:
> > >
> > > public class Param
> > > {
> > > public static void main(String[] args)
> > > {
> > > String temp = null;
> > > manipParameter(temp);
> > > System.out.println("temp = " + temp);
> > > }
> > >
> > > private static void manipParameter(String param)
> > > {
> > > param = "This should be modified";
> > > }
> > > }
> > >
> > > the resulting output would be:
> > >
> > > temp = null
> > >
> > > because Java supports pass-by-value semantics, not pass-by-reference,
> even
> > > for Object-derived types. (This is where Java's insistence that it has
> no
> > > pointers really trips people up.) This means that the POINTER to String,
> > > held by temp, is copied into the String reference named "param", and
> > > subsequent modification of "param" has no effect on the original
> reference
> > > "temp".
> > >
> > > For all you C++-heads out there, the difference is one of
> > >
> > > void manipParameter(String* pString); // THIS is what Java does,
> effectively
> > >
> > > vs.
> > >
> > > void manipParameter(String& pString); // THIS is NOT what Java does
> > >
> > > Hence, Shiraz is correct in that the *parameter*, temp, (not the lvalue
> of
> > > the return value's assignment) will not be modified.
> > >
> > > However, because the original code was written to not only use the
> (wrongly)
> > > assumed pass-by-reference semantics, but also to copy the return value
> into
> > > temp:
> > >
> > > In short, everybody's right, bur for different reasons. :)
> > >
> > > Ted Neward
> > > Patterns/C++/Java/CORBA/EJB/COM-DCOM spoken here
> > > http://www.javageeks.com/~tneward
> > > "I don't even speak for myself; my wife won't let me." --Me
> >
> >
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