Alternative to superclass field

Question

public class CustomNode extends GuiObject {

    public void doSomethingWithBase() {
        Pane base = getBase();
        //The problem is here, base can only be VBox or HBox, but
        //accessing it as a Pane removes a couple of needed features like
        //setFillHeight(boolean val), etc
        //I can do casting here (to VBox or HBox), but it doesn't look too elegant
        //Any alternatives?
    }

}

public abstract class GuiObject {

    private final Pane base;

    public Pane getBase() {
        return base;
    }

}

In doSomethingWithBase() I need to process base which can only be VBox or HBox, but I'm forced to use a superclass to get it, but also I'm forced to do casting, which I don't prefer.

Is there any alternative to casting here?

Add generics to GuiObject so you will have class of base in CustomNode — Boris Chistov, Jun 08 '20 at 12:59
You said that you are going to use `setFillHeight`, but that's only available in `HBox`, what if `base` is a `VBox`? Are you going to use `setFillWidth` instead? — Sweeper, Jun 08 '20 at 13:02
@Sweeper Yeah, that was just an example, if `base` is a VBox I'd use `setFillWidth` — ImNotARobot, Jun 08 '20 at 13:04

TomStroemer · Accepted Answer · 2020-06-08T13:05:14.510

2

If you only have HBox or VBox in doSomethingWithBase you can use generics. Would look like this:

public class CustomNode extends GuiObject<VBox> {

    public void doSomethingWithBase() {
        VBox base = getBase();
        //The problem is here, base can only be VBox or HBox, but
        //accessing it as a Pane removes a couple of needed features like
        //setFillHeight(boolean val), etc
        //I can do casting here (to VBox or HBox), but it doesn't look too elegant
        //Any alternatives?
    }

}

public abstract class GuiObject<P extends Pane> {

    private final P base;

    public P getBase() {
        return base;
    }

}

If you have both VBox and HBox in doSomethingWithBase then the question is - how do you know what you get?

edited Jun 08 '20 at 13:05

answered Jun 08 '20 at 12:59

TomStroemer

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Btw. Is `P` in `
` correct naming? Can you please send me a source?
– ImNotARobot Jun 08 '20 at 13:06
1

Well, dependens on what naming conventions you use. For a discussion about this read here: https://stackoverflow.com/questions/2900881/generic-type-parameter-naming-convention-for-java-with-multiple-chars – TomStroemer Jun 08 '20 at 13:12
@TomStroemer Thank you for useful link, I'd rather stay with `T` though – ImNotARobot Jun 08 '20 at 13:17

Alternative to superclass field

1 Answers1