Question

I have tree classes.

class MyObject{
    public void DoSomething()
    {
        here I need to call method add from class base.
    }
}

class base
{
    protected final void add(){}      
}

class extended extends base {
    private MyObject pObject = new MyObject();
    ...
    {
        pObject.DoSomething();
    }
}

I could have created class for each variation that extends class extended, but the type what I need to use becomes available only after class extended is already initiated.

How do I call base.add() from MyObject inner method?

Answer 1

You can do it in a couple of ways:

• Have a reference of your extended class in MyObject class. When you instantiate MyObject variable in extended class, pass it the reference of extended.

Something like this:

class MyObject{
    private base baseObj;

    public MyObject(base baseObj){
        this.baseObj = baseObj;
    }

    public void DoSomething()
    {
        //here I need to call method add from class base.
            //use baseObj to call the methods
    }
}


class base
{
    protected final void add(){}      
}


class extended extends base {
    private MyObject pObject;
    ...

    public extended(){
        pObject = new MyObject(this);
    }

    {
        pObject.DoSomething();
    }
}

• Declare the methods in base class static. This way you can call the methods without requiring an instance of the base class.

Something like this:

class MyObject{

    public void DoSomething()
    {
        //here I need to call method add from class base.
        //call like this
        base.add();
    }
}


class base
{
    protected static final void add(){}      
}


class extended extends base {
    private MyObject pObject;
    ...

    public extended(){
        pObject = new MyObject(this);
    }

    {
        pObject.DoSomething();
    }
}

One more thing: This is off-topic, but you might want to read about Java Naming Conventions. Having class names start with lowercase is something that you wouldn’t find in the naming conventions.