Java AWT GridLayout create calculator

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.GridLayout;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Main {

   public static void main(String[] args) {
      JFrame frame = new JFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setTitle("GridLayout frame");

      JPanel buttonPanel = new JPanel();
      buttonPanel.setLayout(new GridLayout(4, 4));
      //from   w  w  w .j  a v a2 s .  c o  m
      addButtons(buttonPanel, 
         "7", "8", "9", "0", "4", "5", "6", "C",
         "1", "2", "3", "=", "+", "-", "*", "/"
      );
      
      JTextField resultBox = new JTextField("*** Layout Only ***");
      resultBox.setEditable(false); // Prevent user editing
      
      frame.getContentPane().add(buttonPanel, BorderLayout.CENTER);
      frame.getContentPane().add(resultBox, BorderLayout.NORTH);

      frame.pack();
      frame.setVisible(true);
   }

   private static void addButtons(Container contentPane, String... strings) {
      for (String label : strings) {
         contentPane.add(new JButton(label));
      }
   }
}

import java.awt.GridLayout;

import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Main extends JFrame {
  private static final String[] names = { "7", "8", "9", "/", "4", "5", "6", "*", "1", "2", "3", "-", "0", ".", "=",
      "+" };//from w w w  . j  a v  a2s .co m

  public Main() {

    JPanel container = new JPanel();
    JPanel topGrid = new JPanel(new GridLayout(1, 1));
    JPanel bottomGrid = new JPanel(new GridLayout(4, 4, 3, 3));

    container.setLayout(new BoxLayout(container, BoxLayout.Y_AXIS));

    topGrid.add(new JTextField(10));

    // add buttons
    for (int i = 0; i < names.length; i++) {
      bottomGrid.add(new JButton(names[i]));
    }

    container.add(topGrid);
    container.add(bottomGrid);

    add(container);
  }

  public static void main(String[] args) {
    Main gui = new Main();
    gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    gui.setSize(250, 250);
    gui.setVisible(true);
  }
}