GUI JFrame background color change - user-interface

Question

I've revisited this post. I have been able to upload the text file, create a GUI, populate the GUI with JRadioButtons that are labeled from the text file...
Now, I cannot get the background to change color when the JRadioButton is selected! I know that it has something to do with the ActionListener, but how do I fix this? The color needs to be implemented from the hex color code.
public class FP extends JFrame implements ActionListener {
TreeMap<String, String> buttonMap = new TreeMap <>();
// Constructor
#SuppressWarnings("empty-statement")
public FP() throws IOException {
JPanel panel = new JPanel();
add(panel, BorderLayout.CENTER);
panel.setBorder(new TitledBorder("Pick a Radio Button!"));
JRadioButton[] btnArray = new JRadioButton[20];
ButtonGroup btnGroup = new ButtonGroup();
BufferedReader reader;
reader = new BufferedReader(new FileReader("src/colors.txt"));
String currentLine = reader.readLine();
while (currentLine != null) {
String[] pair = currentLine.split("\\s+");
buttonMap.put(pair[0],pair[1]);
currentLine = reader.readLine();
}
//check retrieving values from the buttonMap
for(Map.Entry<String,String> entry : buttonMap.entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
}
for (int i = 0; i<20; i++){
for(Map.Entry<String, String> entry : buttonMap.entrySet()){
JRadioButton rb = new JRadioButton(entry.getKey() + " " + entry.getValue());
panel.add(rb);
btnGroup.add(rb);
rb.addActionListener(this);
}
}
//private final JRadioButton btnMale = new JRadioButton("Male")
Collection bMapIt = buttonMap.entrySet();
Iterator it = bMapIt.iterator();
System.out.println("Colors and codes");
while(it.hasNext())
System.out.println(it.next());
}
#Override
public void actionPerformed(ActionEvent e) {
setBackground(Color.decode(buttonMap.get(e)));
}
public static void main(String[] args) throws IOException {
FP frame = new FP();
frame.setVisible(true);
frame.setSize(350, 240);
frame.setTitle("Final Project");
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

Answer 1

for(Map.Entry<String, String> entry : buttonMap.entrySet()){
for (int i = 0; i<1; i++){
btnArray[i] = new JRadioButton(entry.getKey() + " " + entry.getValue());
panel.add(btnArray[i]);
btnGroup.add(btnArray[i]);
btnArray[i].addActionListener((ActionEvent e) -> {
String btnColor = buttonMap.get(((JRadioButton) e.getSource()).getText());
String hexColor = entry.getValue();
System.out.println(hexColor);
panel.setBackground(Color.decode("#"+hexColor));
});
}
}
This with the addition of class....
#Override
public void actionPerformed(ActionEvent e) {}
}