Here is a code that displays button, table and jcombobox.

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

public class SimpleJTableExample{
  public static void main(String[] args){
  new SimpleJTableExample();
  }

  public SimpleJTableExample(){
  JFrame frame = new JFrame("Creating JTable Component Example!");
  JPanel panel = new JPanel();
  String data[][] = {{"A","Delhi","1111"},{"B","Mumbai","2222"},
   {"C","Kolkata","3333"},{"D","Chennai","4444"}};

    String col[] = {"Name","Address","Contact No"};

  JTable table = new JTable(data,col);
  table.getTableHeader().setReorderingAllowed(false) ;
  table.getTableHeader().setResizingAllowed(false);

 panel.add(table.getTableHeader() , BorderLayout.NORTH);
 panel.add(table, BorderLayout.CENTER);

  JPanel pan = new JPanel(new GridLayout(2,2));
  JLabel l=new JLabel("Select");
  JComboBox combo=new JComboBox();
  combo.addItem("A");
  combo.addItem("B");
  combo.addItem("C");
  combo.addItem("D");
  JButton b=new JButton("Submit");
  pan.add(l);
  pan.add(combo);
  pan.add(b);

  frame.add(pan,BorderLayout.NORTH);
  frame.add(panel,BorderLayout.SOUTH);
  frame.setSize(300,200);
  frame.setVisible(true);
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }
}