How to cast objects in an array with multiple classes?

Question

I have an array of JComponent objects containing JTextField and JComboBox objects. I chose to make one array instead of two for more efficiency. But if I iterate over the objects I can't seem to cast them correctly, since my IDE doesn't recognize the .setText() method in the last line of the example code. How do I cast the items properly?

JComponent[] items = {JTextField1, JComboBox1};
for (JComponent item : items) {
    if (item instanceof JTextField) {
        item = (JTextField) item;
        item.setText(null);
    }
    else {
        item = (JComboBox) item ;
        item.setSelectedIndex(-1);
    }
}

tfosra · Accepted Answer · 2016-05-20 18:29:46Z

4

Do it simpy like this

if (item instanceof JTextField) {
    ((JTextField) item).setText(null);
}
else {
    ((JComboBox) item).setSelectedIndex(-1);
}

Explanation

When you are iterating over your List, every item variable is saw as a JComponent. But what you need is to call a method for a specific subtype (e.g JTextField). So the solution is just to cast that item variable into the specific Subtype before calling your desired method.

edited May 20, 2016 at 18:29

answered May 20, 2016 at 17:11

tfosra

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1 Comment

VGR Over a year ago

This would be a better answer if you explained why you did it that way, instead of just writing the code for him.

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