What is passing by value?

What does it mean that Java is pass by value?

See this JavaRanch campfire story: Pass by value.

Thanks, pretty helpful. Another question re:

"In line 1, a cup called x, of size int, is created and given the value 3.

In line 2, a cup called y, of size int, is created and given the value... 3.

The x variable is not affected!

Java COPIES the value of x (which is 3) and puts that COPY into y. "

So in Java, if I type int x = 3, int y = x, it COPIES whatever x is and puts it into y. It's as if I right clicked on x and pasted it to y, right? How would I have y reference x, as in if I changed x it would also change y? (Like in excel when you reference another cell and change that cell...)

Originally posted by Jake Miller:
...How would I have y reference x, as in if I changed x it would also change y? (Like in excel when you reference another cell and change that cell...)

That's a good question.

You cannot do this with Java primitive types, because the value itself is simply copied to the new variable. But if you want y to change whenever x changes, then maybe you don't need y at all. Just use x.

A more elaborate approach would be to replace y with a method that "gets" the current value of x when needed. This might be appropriate if x is an instance variable of some other object.

Originally posted by marc weber:

But if you want y to change whenever x changes, then maybe you don't need y at all. Just use x.

Oh yea. You could do that huh