ProvaModularJFrame.java

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;

import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JFrame;

public class ShumlabsFrame extends JFrame {

    private static final long serialVersionUID = 1L;
    JButton btnAplicar = new JButton("Aplicar mudanca");

    public ShumlabsFrame(String name) {
        super(name);
        Container pane = this.getContentPane();
        btnAplicar.addActionListener(e -> processEvent(e));
        pane.add(btnAplicar, BorderLayout.SOUTH);
    }

    public void processEvent(Action e) {
        this.setBackground(Color.BLUE);
        this.setOpacity(1);
    }
    
    public static void main(String[] args) {
        ShumlabsFrame frame = new ShumlabsFrame("Shumlabs Frame");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }
}