Swing_Simple_Base_Program_Structures/CustomJPanel/MyJPanel.java

package CustomJPanel;

import java.awt.FlowLayout;

import javax.swing.JButton;
import javax.swing.JPanel;

public class MyJPanel extends JPanel {
    private int counter;

    public MyJPanel() {
        super();

        counter = 0;

        this.setLayout(new FlowLayout(FlowLayout.CENTER));
        this.setSize(300, 200);

        JButton button = new JButton();
        button.setText("Click Me!");
        button.addActionListener((v) -> {
            counter += 1;

            button.setText("You've clicked the button " + counter + " times!");
        });

        this.add(button);
    }
}