[RESOLVED] inheritance - a beginner's question

Ello,

If class "widget", extends "something", is it possible to create an instance of something then use it it as a widget?

Here's the code I'm trying to get to work:

VB Code:

class universe
{
    public static void main(String[] args)
    {
        something whoKnows; 
        whoKnows = new widget();
        System.out.println(whoKnows.getWeight());
    }
}
 
class something
{
    public int weight=2;
    
}
 
class widget extends something
{
    public int getWeight()
    {
        return weight;
    }
}

Output:

Quote:

---

C:\JAVA\INHERI~1>javac universe.java
universe.java:8: cannot find symbol
symbol : method getWeight()
location: class something
System.out.println((widget)whoKnows.getWeight());
^
1 error

---

Thanks!

Quote:

---

Originally Posted by Evil_Cowgod

If class "widget", extends "something", is it possible to create an instance of something then use it it as a widget?

---

No, that would be backward inheritance :)

In an inheritance chain, if extending a class is going downwards, classes are "upwards" compatable, but not downwards, if you see what I mean. So if widget extends something you can use a widget instance as a something instance but not the other way round.

If you override a something method in widget then you may alter the behaviour, but you can't remove a method from a class.

Ok, thanks :thumb: