GUI Grid Java

/*
 The buttons that the user interacts with need to be made, but
 since we don't know how many we need, they have to be named first.
  So right below the line where you create frame create the
 buttons: JButton[][] grid; The two sets of square brackets are
 there to say that the JButton's in the grid are kept in a
 two-dimensional format, if there were only one set of square
 brackets then it would simply be a line of JButton's, which
 still works, it's just easier to reference which button is being
  created or interacted with when it's two-dimensional.

The JButton's have been named, but we still have to say how many
buttons there are. You need to add a line of code in the
constructor that sets the amount: grid=new JButton[width][length];

Now that it's been determined that there will be a certain number
of buttons, each must be created. The easiest way to do this is
with two for loops, one for the x-axis, one for the y-axis. Inside
 the two loops we make a new button, and for ease of reference the
  example puts text inside each button so we know which button in
  the two-dimensional array is where. To create a button, inside
  the loop you need to put grid[x][y] = new JButton ("("+x+","+y+")");
 */

/*
 LINKS:
 http://www.wikihow.com/Make-a-GUI-Grid-in-Java
 https://stackoverflow.com/questions/144892/how-to-centre-a-window-in-java
*/

package com.samkough.main;

import javax.swing.JFrame;
import javax.swing.JButton;
import java.awt.GridLayout;

public class Grid
{
	JFrame frame = new JFrame(); // creates frame
	JButton[][] grid; // names the grid of buttons

	public Grid(int width, int length)
	{
		// Sets the layout of frame
		frame.setLayout(new GridLayout(width, length));
		// Makes the frame close when you hit the 'x'
		// button in the top right hand corner
		grid = new JButton[width][length]; // allocate the size of grid
		for (int y = 0; y < length; y++)
		{
			for(int x = 0; x < width; x++)
			{
				grid[x][y] = new JButton("("+x+", "+y+")");
				frame.add(grid[x][y]); // adds button to grid
			}
		}
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		// Sets size of frame
		frame.setSize(800, 800);
		// Sets the frame visible
		frame.setVisible(true);
		frame.setLocationRelativeTo(null);
		frame.setTitle("GUI Grid");

		for (int y = 0; y < length; y++)
		{
			for (int x = 0; x < width; x++)
			{
				grid[x][y] = new JButton("("+x+", "+y+")");
				frame.add(grid[x][y]); // adds button to grid
			}
		}
	}

	public static void main(String args[])
	{
		new Grid(3,3); //makes new Grid with 2 parameters
	}
}