I need help incorporating the buttons, when the user clicks the button, it should display in the textfield. How do I do this? I am using GUI. Any help would be appreciated. Here is the code:

import TerminalIO.KeyboardReader;
import javax.swing.*;
import BreezySwing.*;

public class Calculator extends GBFrame {

// declare variables for the window objects
private DoubleField ansField;
private JButton oneButton;
private JButton twoButton;
private JButton threeButton;
private JButton fouButton;
private JButton fivButton;
private JButton sixButton;
private JButton sevButton;
private JButton eigButton;
private JButton ninButton;
private JButton zerButton;
private JButton addiButton;
private JButton subButton;
private JButton mulButton;
private JButton divButton;
private JButton dotButton;

// Constructor
public Calculator(){

// Instantiate and add window objects to the window
ansField = addDoubleField (0, 1,1,4,1);

oneButton = addButton ("1", 4,1,1,1);
twoButton = addButton ("2", 4,2,1,1);
threeButton = addButton ("3", 4,3,1,1);
fouButton = addButton ("4", 3,1,1,1);
fivButton = addButton ("5", 3,2,1,1);
sixButton = addButton ("6", 3,3,1,1);
sevButton = addButton ("7", 2,1,1,1);
eigButton = addButton ("8", 2,2,1,1);
ninButton = addButton ("9", 2,3,1,1);
zerButton = addButton ("0", 5,3,1,1);
addiButton = addButton ("+", 2,4,1,1);
subButton = addButton ("-", 3,4,1,1);
mulButton = addButton ("*", 4,4,1,1);
divButton = addButton ("/", 5,4,1,1);
dotButton = addButton (".", 5,2,1,1);
}


Respond to button click events
public void buttonClicked (JButton buttonObj){
// Local variables
Calculator calculate = new Calculator();

// Determine which button was clicked
if (buttonObj == addButton){
calculate.setCalculate(ansField.getNumber());

}
}


// Execution begins in the method main as asual.
public static void main (String [] args) {
Calculator theGUI = new Calculator();
theGUI.setSize (250, 250);
theGUI.setVisible (true);

}
}