Question

I want to have a base class and a couple of classes extending it.

Then I want to have an array that could be either of the two extending classes.

I was hoping to do something like this:

class Base{  }
class A extends Base {}
class B extends Base {}

then I want an array that could be either A or B so I use Base in array declaration

Base[] it = Base[2];

it[0] = new A();
it[1] = new B();

I’m not sure if I’m doing this correctly or if this allowed.

Thanks

Answer 1

You are missing the new keyword:

Base[] it = new Base[2];

Other then that – the approach is just fine. An array of type Base[] can hold objects of type A and B, since they are themselves extending the type Base.

Example:

static public class Base { 
    public void foo() { 
        System.out.println("I am base");
    }
}
static public class A extends Base { 
    @Override
    public void foo() { 
        System.out.println("I am A");
    }
}
static public class B extends Base { 
    @Override
    public void foo() { 
        System.out.println("I am B");
    }
}

    public static void main(String[] args) {
        Base[] arr = new Base[2];
        arr[0] = new A();
        arr[1] = new B();
        arr[0].foo();
        arr[1].foo();
    }

Will result, as expected in printing:

I am A
I am B