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Issue with numbers not appearing in box when respective button is pressed

I'm making a simple calculator in GUI and I have all the code typed and ready, but I'm having trouble with making it so that when the user presses a number button, the respective number appears in the text box above. Do I need to use a radio button? Thanks in advance
I've tried action listeners but they didn't work (or I'm probably using them incorrectly). I've put the code for the 1 button.
JButton num1 = new JButton("1");
num1 = b1;
num1.setSize(50,50);
num1.setLocation(20,200);
num1.setBackground(Color.WHITE);
num1.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e)
{

Just append the number to the JTextField(using setText(String) and getText()) in the actionPerformed function.

Having trouble giving my JPanel functionality

*This is my first time using GUI, I seem to miss something my eye can't catch. The code looks fine to me however when i submit it to autoLab I get this error, which I cannot figure out where I went wrong.
{"correct":false,"feedback":"(class java.lang.NumberFormatException)
Error while attempting to call static method q2() on input [1]}
The problem question is q5:
Write a public static method named q5 that takes no parameters and returns a JPanel.
The panel will contain 1 JTextField with any number of columns, 1 JButton with any label,
and 1 JLabel. The panel will have functionality such that when a user enters a number into
the text field (we'll call this value x) and presses the button the label will display the
y-value of a parabola in standard form (https://www.desmos.com/calculator/zukjgk9iry)
where a=5.37, b=-6.07, and c=2.0 at the x-value from the text field
Hint: If you store y in the wrapper class Double instead of the primitive double you can
call toString on it to convert it to a string that can be used as the text for the label
Tip: After clicking the button you may have to resize your window to see the result since
the frame will not automatically resize to fit the new text
Do not create any JFrames in your problem set questions. Doing so will crash the
auto-grader since the grading server does not have a screen to display the JFrame.
Instead, only return the required JPanel in the problem set methods and test with a JFrame
in your main method, or other helper methods that are not graded
This is the code I wrote
public static JPanel q5() {
JPanel panel = new JPanel();
JTextField textField = new JTextField(5);
panel.add(textField);
JLabel label = new JLabel("hello!");
panel.add(label);
JButton button = new JButton("Click Me!");
panel.add(button);
button.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent e){
int x = Integer.parseInt(textField.getText());
double a=5.37*Math.pow(x, 2);
double b=-6.07*x;
double c=2.0;
String answer= ("y = " + a+ b +c);
label.setText(answer);
}
});
return panel;
}
can you explain where I went wrong , thank you.

So, a NumberFormatException can occur when trying to parse a String, when the String does not contain a number. You did not give enough information to be sure, but I am going to presume that it is this line that causes the problem:
int x = Integer.parseInt(textField.getText());
One thing that strikes me as odd, is that you initialize the JTextField with 5 columns:
JTextField textField = new JTextField(5);
Is that what you want? If you wanted to pre-initialize the text field with a value of 5, you would have to do it like this:
JTextField textField = new JTextField("5");

how to identify a button in a group of loop generated buttons?

I have a group of loop generated buttons made with this code
this.panelCuerpo.setLayout(new GridLayout(4,5));
for(int i = 1; i<=20; i++){
final JToggleButton b = new JToggleButton(new ImageIcon("/images/available.png"));
panelCuerpo.add(b);
b.setIcon(new javax.swing.ImageIcon(getClass().getResource("/Images/available1.png")));
b.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent evt){
if(b.isSelected()){
b.setIcon(new javax.swing.ImageIcon(getClass().getResource("/Images/busy1.png")));
cantidadBoletas++;
}else{
b.setIcon(new javax.swing.ImageIcon(getClass().getResource("/Images/available1.png")));
cantidadBoletas--;
}
System.out.println(cantidadBoletas);
}
});
}
The problem here is that I can't use setText() to compare later cause there's no property to hide that text. How can I compare it later?
PS. Each button has a consecutive number, it's easy to assign that number. The real problem lies in where to put it.

You could:
Use the Action API, which lets you trigger the selected state of the associated button. This allows you to de-couple the button from the underlying "action" it should take. Take a look at How to Use ActionsHow to Use Actions for more details
Use the actionCommand property of the JButton. This allows you to have some kind of "identifier" associated with the button which is independent of the text
Use an array or List to maintain a reference to the buttons

You can maintain a List<JToggleButton> of JToggleButton and fetch element later by the index. Apart from that instead of adding ActionListener in loop you can implement ActionListener which can be used for all buttons and you just need to write b.addActionListener(this); in loop.
NOTE : better to start from i = 0 instead of 1

How to update JLabel from action listener?

Explanation:
I have an int variable to keep track of how many times button is pushed.
I have a JLabel that shows this variable in the form of a string basically.
When I click Add, I want the variable to update and then the jlabel to show the updated variable.
I have a secondary button listener class that implements the actionlistener code. I can't post all my code because my professor is strict about her plagiarism checks.
EDIT:
I see when I add the JLabel.setText to the action listener, it will update. Not sure if this is the best method.
Code:
int counter = 0;
JLabel label = new JLabel("Count is: " + counter);
JButton increment = new JButton("Increment Here");
increment.addActionListener(new ButtonListener());
My button listener class contains this code:
counter++;
Let me know if more code is necessary, I am just trying to simplify my issue. I tried adding an UpdateUI(); method, but nothing happened.

in your Button Action Listener
Write
label.setText("Count is: " + counter);
After the Increment to count variable

Array of buttons, make only one button change its text when clicked

I have an array I fill with buttons and I want an individual button to change its text when clicked.
for (int i = 0; i<4; i++)
{
button[i] = new JButton ("Add");
button[i].addActionListener(this);
box[i] = new JComboBox();
foodOptions.add(box[i]);
foodOptions.add(button[i]);
}
public void actionPerformed (ActionEvent e)
{
button[this].setText("I've been clicked!");
}
The current doesn't work because of incompatible types, what format is appropriate?

Yes, it makes no sense to pass an object, this, into an array index which expects an int, not your GUI object, so I'm not sure what you were trying to achieve with this.
Just get a reference to the JButton that's been clicked from the ActionEvent's getSource() method:
JButton btn = (JButton)e.getSource();
btn.setText("I've been clicked");
Edit:
Also you should avoid using this as your ActionListener since this means that you're likely having your GUI class implement an ActionListener which is asking the poor class to be too many things, to do too much. You're much better off either using anonymous inner classes or else even better use AbstractActions.