Help with Swing

I am trying to make a calculator. I am just trying to setup the GUI first. The problem I am having is that I want the JTextField to be the full width of the pane above all the JButtons. I want the double zero button to take up the space of two buttons horizontally in the bottom left
corner. I want the enter button to take up the space of two Jbuttons vertically in the bottom right hand corner. Here is a pic of what my UI looks like right now:
Attachment 786

Here is my code:

Code :

---

public class KeypadUse
{
	public static void main(String[] args)
	{
		Keypad key = new Keypad();
	}
}

---

Code :

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import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
public class Keypad extends JFrame
{
	private JTextField displayTF;
	private JButton oneB, twoB, threeB, fourB, fiveB, sixB, sevenB, eightB, nineB, zeroB,
				doubleZeroB, plusB, minusB, enterB;
 
	public Keypad()
	{
		setTitle("Keypad");
		Container pane = getContentPane();
		pane.setLayout(new GridLayout(5, 4));
 
		displayTF = new JTextField(20);
		oneB = new JButton();
		twoB = new JButton();
		threeB = new JButton();
		fourB = new JButton();
		fiveB = new JButton();
		sixB = new JButton();
		sevenB = new JButton();
		eightB = new JButton();
		nineB = new JButton();
		zeroB = new JButton();
		doubleZeroB = new JButton();
		plusB = new JButton();
		minusB = new JButton();
		enterB = new JButton();
 
		pane.add(displayTF);
		pane.add(minusB);
		pane.add(nineB);
		pane.add(eightB);
		pane.add(sevenB);
		pane.add(plusB);
		pane.add(sixB);
		pane.add(fiveB);
		pane.add(fourB);
		pane.add(enterB);
		pane.add(threeB);
		pane.add(twoB);
		pane.add(oneB);
		pane.add(zeroB);
		pane.add(doubleZeroB);
 
		setSize(500,500);
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		setVisible(true);
	}
 
}

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what I was thinking is that maybe there is a way to put a "place holder" to take up a full row and then I can resize my textfield. But I am
stumped on the buttons.

thanks in advance!

use gridbag layout!! that will surely help!
click here to know more!