It doesn't display the result in the text field. If I entered 9 and pressed the square root button the text field still has 9 in it.

We did arrays before gui but the sample that he showed us is like that for declaring buttons. I've seen codes for calculators and declaration for buttons is in array form. I would really want to do that but maybe after I submit this to him.
By the way I finally solved the problem that I posted. But I got another problem I added a few lines of codes but it doesn't perform the sqrt function. I really need help for this, I'm not really good in programming but I'm trying to learn things little by little. Hope you can help me with this.
Here's the line that I added:

else if(e.getSource() == bSqrt)
			{
			result = Math.sqrt(Double.parseDouble(tf1.getText()));
			tf1.setText(new Double(result).toString());
			secondNum = false;
			}

True it would really trim down lines of code, but I wanted to stick with what my professor taught me since I don't want to start a discussion of "not being the author of my code."

But after I submit this calculator, I would change it into an array

It didn't work but I got an idea on how to do it. ) Thank you, for welcoming me here!

There's an option in my code for multiple times of pressing equal sign and for pressing it once. But
if I press a number button the text field should reset and place the value of the number button that I pressed. In my code the latter thing doesn't happens.