How do I get which JRadioButton is selected from a ButtonGroup

You must add setActionCommand to the JRadioButton then just do:

String entree = entreeGroup.getSelection().getActionCommand();

Example:

java = new JRadioButton("Java");
java.setActionCommand("Java");
c = new JRadioButton("C/C++");
c.setActionCommand("c");
System.out.println("Selected Radio Button: " + 
                    buttonGroup.getSelection().getActionCommand());

I would just loop through your JRadioButtons and call isSelected(). If you really want to go from the ButtonGroup you can only get to the models. You could match the models to the buttons, but then if you have access to the buttons, why not use them directly?

I got similar problem and solved with this:

import java.util.Enumeration;
import javax.swing.AbstractButton;
import javax.swing.ButtonGroup;

public class GroupButtonUtils {

    public String getSelectedButtonText(ButtonGroup buttonGroup) {
        for (Enumeration<AbstractButton> buttons = buttonGroup.getElements(); buttons.hasMoreElements();) {
            AbstractButton button = buttons.nextElement();

            if (button.isSelected()) {
                return button.getText();
            }
        }

        return null;
    }
}

It returns the text of the selected button.