Check out example codes for "java simple jframe example". It will help you in understanding the concepts better.

Code Example 1

import javax.swing.*;
import java.awt.FlowLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.*;
 
public class JFrameExample{
     
    public static void main(String[] args){
        // Create frame with title Registration Demo
        JFrame frame= new JFrame(); 
        frame.setTitle("JFrame Demo");
        frame.pack();
        frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

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