Java - pass a pointer to an object to a function

Question

What I want to achieve is something like this:

MyClass object = null;
doStuff(&object);

// `object` can now be non-null

---

What I'm currently doing is this, but I think there must be a better way to achieve this behavior in Java:

MyClassPointer pointer = new MyClassPointer(null);
// pointer.object is null
doStuff(pointer);

// pointer.object can now be non-null

Solution 1

If you really want doStuff to return two values: There may well be a better way to design this. Nevertheless, if you've decided that having doStuff return two values is really the best design, it can be done with a simple helper class:

static class MyClassAndBoolean {
    public MyClass obj;
    public boolean b;
    public MyClassAndBoolean(MyClass obj, boolean b) { this.obj = obj; this.b = b; }
}

and then change doStuff's return type to MyClassAndBoolean. This is one of the very few cases where I think public fields in a class are OK. Since you're defining a simple class just to use as a function result, rather than representing a coherent concept, the usual concerns about defining accessors instead of exposing fields, etc., don't really apply. (P.S. I just guessed at boolean for the other type, but it can be anything, of course.)

Another workaround:

MyClass[] obj = new MyClass[1];
result = doStuff(obj);

Change doStuff's parameter type to MyClass[], and have it stuff the new object into parameter[0]. I do see this idiom used in some of the Java and Android library methods.

Solution 2

Why not simply:

MyClass object = doStuff();

which is much more intuitive IMHO. Otherwise you have to pass a reference (not pointer!) to a container object to your method, as you've identified. That's not a common pattern in the Java world.