Java - Parameter and Enhanced For Loop copy issue

Question

assume i have code like this;

public void insert(Student[] stus)
{
    int count = 0;
    for(Student s: stus)
    {
    s.setId( bla bla);
    stus[count].setId(bla bla) // is this line needed?
    count++;
    }
}

So if i change anything on s from enhanced for loop, can i see the change in stus array also? How does enhanced for loop copy works in parameters or other things etc?

Answer 1

The enhanced for loop doesn't create a copy of the elements of the Collection or array you are iterating over, and therefore s.setId() and stus[count].setId() would update the same Student instance.

stus[count].setId(bla bla) is not needed, as s.setId(bla bla) does the same.

Answer 2

Yes - s is just a variable which contains a value copied from stus. That value is a reference to an object - changes made via s will still be visible from stus. It's only the reference that's copied. So your loop can just be:

for (Student s : stus) {
    s.setId(...);
}

No need for the count at all unless it's part of the computation of the ID. If it is part of that computation, I'd just use a regular for loop instead:

for (int i = 0; i < stus.length; i++) {
    s.setId(/* some expression involving i */);
}