How can I find a button source in AWT?

We were asked to make a simple GUI calculator, and I used getSource() to detect the buttons, because that's what they taught us. It works by typing the first and second value and then choosing the operation. It worked.

But I made a mistake, because they want us to make the numbers also be buttons, just like a real calculator. So how do I get the value of each button using getSource()? Like when I press button 1 and 2 is equal to 3. Here's what I've done:

import java.awt.*;
import java.awt.event.*;

public class SimpleCalculator implements ActionListener
{
    // Containers
    private Frame f;
    private Panel p1, p2, p3, p4;

    // Components
    private Label l1, l2, l3;
    private TextField tf1, tf2, tf3;
    private Button bAdd, bSub, bMul, bDiv, bClear;

    public SimpleCalculator()
    {
        f = new Frame("My First GUI App");

        p1 = new Panel();
        p2 = new Panel();
        p3 = new Panel();
        p4 = new Panel();

        l1 = new Label("First: ");
        l2 = new Label("Second: ");
        l3 = new Label("Result: ");

        tf1 = new TextField(15);
        tf2 = new TextField(15);
        tf3 = new TextField(15);

        bAdd = new Button("+");
        bSub = new Button("-");
        bMul = new Button("*");
        bDiv = new Button("/");
        bClear = new Button("C");
    }

    public void launchFrame()
    {
        // Use the default layout manager of the Panel (FlowLayout)
        p1.add(l1);
        p1.add(tf1);

        p2.add(l2);
        p2.add(tf2);

        p3.add(l3);
        p3.add(tf3);

        p4.add(bAdd);
        p4.add(bSub);
        p4.add(bMul);
        p4.add(bDiv);
        p4.add(bClear);

        // Change the layout manager of the Frame.
        // Use GridLayout(4, 1)
        f.setLayout(new GridLayout(4, 1));

        f.add(p1);
        f.add(p2);
        f.add(p3);
        f.add(p4);