Package

Main.java

import pack.*;
import javax.swing.*;
import java.awt.*;

class Main extends JFrame
{
 public static void main(String[] s)
 {  
  JFrame f1=new JFrame();
  f1.setSize(200,200);
  f1.setBackground(Color.blue);
  f1.setLayout(null);
  f1.setVisible(true);
  f1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
  Pan d1=new Pan(); 
  f1.add(d1);
 }
}

------------------------- Pan.java

package pack;
import javax.swing.*;
import java.awt.*;

public class Pan extends JPanel
{
 JLabel l1;
 public Pan()
 {
  setSize(100,100);
  setLayout(null);
  setBackground(Color.red);
  setVisible(true);
  setBounds(50,50,80,40);
  l1=new JLabel("PANEL");
  l1.setBounds(15,15,50,10);
  add(l1);
 }
}  

Output:-