How to create composite objects

[Roger Chung-Wee]

class A {}
class Composite1
{
    A a = new A();
}
class Composite2
{   
    A a;
    
    void init()
    {
        a = new A();
    }
}
class Composite3
{
    A a;
    
    Composite3()
    {
        a = new A();
    }
}

I'd like to get some views on the best way(s) to create composite objects.
Let's say you need to instantiate class A which is declared in three classes - Composite1, Composite2 and Composite3.
I like Composite1 as member A is valid inside the constructor because it has been initialized at the point of definition.
I think I also like Composite2 (assuming that the init method is invoked after Composite2 has been instantiated). The drawback is that you can't guarantee that init will always be called.
I'm really not sure about Composite3. It will work for a trivial example like this, but is it guaranteed to always work?

[Ahetuki Neti]

Composite1 should be used when the member class A doesn't need parameterised initialization.
Composite2 should be strongly discouraged.
Composite3 is perfect for the situation where the member class A needs a parameter for it's initialization.