Check if entire array is instanceof

Question

I want a Generic Method, however I'm not sure if it's ideal for this scenario, nor am I very much familiar with how Generic's work (if someone could link me a good tutorial or article, I'd very much appreciate it.)

However, I wanted to create a method that handles initialization of JComponents, and if the array of JComponents was All JRadioButtons, to be sent to a different method.

public void initializeComponent(JComponent...components)
{
     if(components[0] instanceof JRadioButton)
         initializeJRadioButtons(components[]);
}

However, this will only check whether the first one is a JRadioButton, I feel Generics may handle this better, but is there a way to check if all components are JRadioButtons without looping?

Such as if someone does this.

JRadioButton[] radioButtons = new JRadioButton[2];
...
initializeComponent(radioButtons);

Maybe you could make the task easier by looping over components, then do instanceof test and delegate to initializeRadioButton (no plural) for each component? Do you need to initialize arrays of components at once? I don't see how generics would help you do that. — Harald K
– Harald K, Commented Mar 3, 2014 at 9:42
@Otanan Yes, figured that out now, too. So you have special methods for initilizing radio buttons, and this and that other stuff, but you want this as an entry method for all those? Why? Also, have you tried just overloading? init(Foo... foos), init(Bar... bars), etc.? — tobias_k
– tobias_k, Commented Mar 3, 2014 at 9:47

Brent Robinson · Accepted Answer · 2014-03-03 09:47:03Z

3

No, you can't check them without looping over them. Consider any process that would do it for you - at some point it would still have to check them one by one as they're distinct objects.

However, what you could do use use method overloading. You could have a method with the signature of

public void initializeComponent(JRadioButton...components)

You then know that every one of those components will be a radio button, hence can skip any checking.

You can then have the method you've already got in your question which may have to check each component to do the correct initialisation.

public void initializeComponent(JComponent...components)

answered Mar 3, 2014 at 9:47

Brent Robinson

2,3961 gold badge20 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Otanan Over a year ago

This is definitely what I might end up using, however, would List<JRadioButton> radioButtons = new ArrayList<>(components); work? Or would I get an exception thrown for trying to add a non JRadioButton to the list if the components array is holding a non-JRadioButton?

Brent Robinson Over a year ago

You'll get a syntax error because you're components variable type is not JRadioButton or a subtype of it (rather a supertype). It'll fail at compile time.

Otanan Over a year ago

Thank you! I can't believe I didn't think of this!

uyuyuy99 · Accepted Answer · 2014-03-03 09:48:51Z

1

I don't see what the problem of looping over the components is:

boolean isRadioButtons = true;
for (Component c : components) {
    if (!(c instanceof JRadioButton)) {
        isRadioButtons = false;
        break;
    }
}

answered Mar 3, 2014 at 9:48

uyuyuy99

3534 silver badges11 bronze badges

Comments

Rohit Jain · Accepted Answer · 2014-03-03 10:05:59Z

Since you just want to check whether the array that is passed is actually a JRadioButton[] array or not, you can use the following code. Although this is a hack, that does the job:

public static void initializeComponent(JComponent... components) throws ClassNotFoundException {
    // Get the Class instance for an array of type JRadioButton.
    Class<?> clazz = Class.forName("[Ljavax.swing.JRadioButton;");

    if (clazz.isInstance(components)) { 
        System.out.println(true);
        initializeJRadioButtons((JRadioButton[]) components);
    }
}

The method uses the encoding for the JRadioButton array to get the Class instance for that type of array. See Class#forName() for more details on this.

If the components is an instance of JRadioButton[], then you'll get true as result. Remember, this is just a hack, as I already said. IMO, overloading is the best option for you.

Xabster · Accepted Answer · 2014-03-03 09:46:55Z

0

No, there is not a built-in way to check if all entries in an array are of a specific sub type type.

Loop it.

answered Mar 3, 2014 at 9:46

Xabster

3,72017 silver badges21 bronze badges

Collectives™ on Stack Overflow

Check if entire array is instanceof

4 Answers 4

3 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related