Java – Action Event.getSource: how to cast properly the source Object

I’m afraid I might make a newbie mistake here. I have ActionListener below, but I get the warning Unchecked cast: 'java.lang.Object' to 'javax.swing.JComboBox<java.lang.String>' stated in if. How do I fix it? I want to call a method API from JComboBox.

I’m not interested in suppressing warnings.

public class MyActionListener implements ActionListener {

@Override
    public void actionPerformed(ActionEvent actionEvent) {
        Object source = actionEvent.getSource();
        JComboBox<String> comboBox;
        if (source instanceof JComboBox) {
            comboBox = (JComboBox<String>) source;
        }
    }

}

To remove the warning without suppression, you will have to compromise with generics and change the code to:

JComboBox<?> comboBox;
if (source instanceof JComboBox) {
    comboBox = (JComboBox<?>) source;
}

If you want to use any method in JComboBox and it uses generic <E>, you can use type conversion there. For example:

String s = (String) comboBox.getItemAt(0);

Explanation:

The warning is issued because the compiler cannot know if your JComboBox exists. is JComboBox<String> or JComboBox<Integer>

Conversion is a runtime thing, and generics in Java are just placeholders to ensure type safety and make the code more readable. With type removal, the compiler updates/modifies all statements involving generics and cast statements when generating bytecode (more information here).