Check out example codes for "java how to make a gui". It will help you in understanding the concepts better.

Code Example 1

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;

public class Foo{

  public static void main(String[] args) {

    JFrame f = new JFrame("A JFrame");
    f.setSize(250, 250);
    f.setLocation(300,200);
    final JTextArea textArea = new JTextArea(10, 40);
    f.getContentPane().add(BorderLayout.CENTER, textArea);
    final JButton button = new JButton("Click Me");
    f.getContentPane().add(BorderLayout.SOUTH, button);
    button.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            textArea.append("Button was clicked\n");

        }
    });

    f.setVisible(true);

  }

}

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