Pass ByRef in Java

[Halsafar]

Okay so far Java is much the same as C syntax and many other respects, not all... Here is one place that is definatly different -- no dynamic memory access em I to imagine? I found myself stuck when trying to play around and learn some stuff on my own. I needed to pass a string by ref so I could alter the value of the passed String object parameter in a function and the original variable would also change. If definetly tried reference & and dereference *.

[CornedBee]

Everything is always passed by reference. However, the String class represents an immutable string - once it has been created, it can't be altered. You can pass a StringBuffer or StringBuilder to the method. Or a StringRef object:

public class StringRef { public String ref; }

Just change the ref object.

[System_Error]

All object variables are references and java does manipulate objects via reference, but arguments are NOT passed by reference, but by value.

[CornedBee]

Whatever ...

[System_Error]

Whatever ...

And you can prove otherwise?

[CornedBee]

No, I know you're right. It just doesn't make much difference whether you consider the objects references passed by value, or the objects passed by reference, since you have no alternative in Java anyway. You cannot pass objects by value, and you can't pass references by reference, and the other two options are semantically equivalent.

[System_Error]

Oh, sorry, thought you were mad or disagreeing

Anways, it doesn't make much sense to me. If you can pass arrays "by reference", then why not other argument types?

[Halsafar]

Okay so I am to assume I cannot write a function to manipulate a passed variable?

Like
public static void Add3To(int iNumToAddThreeTo) {
iNumToAddThreeTo = iNumToAddThreeTo + 3;
}

The original variable passed in won't change?
Well that sucks!

Java keeps creeping along as a very useless language to me. C++ is easily more versitile and structured properly.


In my books:
ByVal == Passes in the value to a new variable parameter
ByRef == Passes in the address to the variable parameter to allow modification of the same place in memory via the parameter.

[System_Error]

Return the object. As for returning multiple objects, I've never run into that situation.

[CornedBee]

I have, once. I handle that by writing a tiny container class.

You can manipulate objects passed to functions, as you are passed a reference to them. But that requires that the objects can be manipulated, which String can't, and neither can the primitive wrappers. You can't change the references themselves. The primitives themselves aren't even objects, and you don't get a reference to them either.

It sounds like a great weakness of the language, but as a matter of fact, the situations where you need it are surprisingly rare.

[Halsafar]

So if I wrote this example using int instead String object, then it is always passed via reference?

[CornedBee]

No, int is a primitive and is passed by value.