create new instance from existing instance and new class instance change existing class params

Question

Let's say we have a setup like this

public class foo {
    int number = 0;
    public void setNumber(int number) {
         this.number = number;
    }
}

public class bar extends foo {
    /* Some other utilities added to the foo class */
    public bar() {
         super();
    }
}

And we have this task running

Scheduler.schedule(1000/* Every second */, () -> {
    fooManager.forEach(f -> System.out.println(f.getNumber()));
})

Now if we do this:

Foo fo = new foo();
fooManager.store(fo);
Bar ba = new bar();

How can I make ba access fo setNumber() method on ba.setNumber() without storing fo in ba and doing ba.getFoInstance().setNumber() and do ba.setNumber() instead

Explanation v2: I want ba.setNumber() to call fa.setNumber()

Looking for something like this: Bar ba = fo but you can't do that since it throws ClassCastException.

Answer 1

It seems to me that what you're trying to achieve is a proxy object. Why shouldn't you want to keep a reference to Foo inside instances of Bar class? It could make sense something like this:

public class Bar extends Foo {

    private Foo fa;

    public bar(Foo fa) {
        super();
        this.fa = fa;
    }

    @Override
    public void setNumber (int number) {
        fa.setNumber(number);
    }

    @Override
    public int getNumber () {
        return fa.getNumber();
    }
}

You should also avoid Bar extending Foo, they should simply both implement the same interface that is sharing the common methods.