create an alias/reference of a variable (JAVA)

Question

I have used a lot of C++ and I am quite confused with the way Java works : if I have a class

public class MyClass{
    private int[] myVariable;
     ...

    public int[] getVar(){
        return myVariable;
    }
}

and then I want to use my variable elsewhere :

public static void main(String[] args){
    MyClass myObject  = new MyClass();
    ...
    int[] temp = myObject.getvariable();
    // use of temp
    ...
}

is temp a copy or a reference of myVariable ?

How do you get a copy / a reference to it ?

Answer 1

There is only one int[] in your example. There is no copying at all. What is returned by the method getVar is a reference to the object.

After the line

int[] temp = myObject.getvariable();

both temp and myVariable are references to the same object. You can test this by doing e.g. temp[0] = 9;. The change will be visible in both places.

If you want to copy an array, you can use one of array.clone(), Arrays.copyOf(array, array.length) or System.arraycopy(...) but none of these are used in your example.

Answer 2

That gets you confused because unlike C, Java is only pass-by-value. So you won't have a reference to that object but only a copy and then if you make any modification to that variable the original won't be affected. See this question for more details: Is Java "pass-by-reference" or "pass-by-value"?

EDIT

To be more specific, in your example you will actually get a reference to the array. But still, that's not like a C pointer. You get a reference only because the actual value you are copying it's a reference itself. As I said, you may find a more detailed explanation about this on the link above.