Question

If I have a class like the one below:

public class Foo()
{
    private RandomObject randomObject = new RandomObject();

    public RandomObject GetRandromObject()
    {
        return randomObject;
    }
}

And in another class I do this:

public class Goo()
{
    private Foo fooObject = new Foo();

    public Goo()
    {
        RandomObject ro = fooObject.GetRandomObject();

        ro.ChangeNumberVariable(23);
    }
}

Will the fooObject have the randomObject NumberVariable changed to 23?

If not would I just have to have a method in Foo called SetRandomObject and just pass in ro? Would this be a good substitute for passing by reference in Java?

What if I just did this:

public class Goo()
{
    private Foo fooObject = new Foo();

    public Goo()
    {
        fooObject.GetRandomObject().ChangeNumberVarialbe(23);
    }
}

Is it still not changing the NumberVariable?

Answer 1

In both cases fooObject.randomObject would have NumberVariable changed to 23. They are pretty much equivalent just the former uses an extra reference.

This does not make Java pass-by-reference. Java is pass by value. Any time you pass something to a method as a parameter it is copied, even if what you pass is a reference to an object.

Though you can use that copied reference to access and mutate the object on the end of it, as you are doing here, any re-assignment of that reference cannot escape the method.

In your first example doing:

ro = new RandomObject();

would not change anything about fooObject.randomObject.