How to output variable in JLabel

Question

I'd like to start off by mentioning this is only my 3rd week of programming and my first question here. I have an assignment where I need to have this program calculate the minimum change for a given number and display the amount of each coin after clicking the calculate button.

My question is where do I need to place the calculations and how to get the resulting variables to output into the quarters/dimes/nickels/pennies JLabel fields on the right side of the GUI.

package mincoinsgui;

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

class MinCoinsGui extends JFrame
{
//init

    private static final int QUARTERS = 25;
    private static final int DIMES = 10;
    private static final int NICKELS = 5;
    private static final int PENNIES = 1;

    int quarters = 0;
    int dimes = 0;
    int nickels = 0;
    int pennies = 0;
    int change = 0;
//text field
    private JTextField changeTF = new JTextField(2);

//main method
    public static void main(String[] args)
    {
//instantiate window object
        MinCoinsGui window = new MinCoinsGui();
        window.setVisible(true);
    }

    //contructor method
    public MinCoinsGui()
    {
        // 1. Create/initialize components
        JButton calculateBtn = new JButton("Calculate");
        calculateBtn.addActionListener(new CalculateBtnListener());

//        JButton clearBtn = new JButton("Clear");
//        clearBtn.addActionListener(new ClearBtnListener());
        changeTF.setEditable(true);

        // 2. Create panel panel / set grid layout
        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(6, 2, 2, 2));

        // 3. Add components to panel panel
        panel.add(new JLabel("Enter Change (1-99):"));
        panel.add(changeTF);
        panel.add(new JLabel("Quarters"));
        panel.add(new JTextField(quarters));
        panel.add(new JLabel("Dimes"));
        panel.add(new JTextField(dimes));
        panel.add(new JLabel("Nickels"));
        panel.add(new JTextField(nickels));
        panel.add(new JLabel("Pennies"));
        panel.add(new JTextField(pennies));
        panel.add(calculateBtn);
        //content.add(clearBtn);

        //set window (JFrame) characteristics
        setContentPane(panel);
        //do layout
        pack();
        setTitle("Minimum Coins");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //center window
        setLocationRelativeTo(null);

    }

    //CalculateBtnListener
    class CalculateBtnListener implements ActionListener
    {

        public void actionPerformed(ActionEvent e)
        {
            String dyStr = changeTF.getText();
            change = Integer.parseInt(dyStr);
            while (change != 0)
            {
                while (change >= 25)
                { //Subtact & Count Quarters
                    change = change - QUARTERS;
                    quarters++;
                } //Subtract & Count Dimes
                while (change >= 10)
                {
                    change = change - DIMES;
                    dimes++;
                } //Subtract & Count Nickels
                while (change >= 5)
                {
                    change = change - NICKELS;
                    nickels++;
                }
                pennies = change;
            }

        }
    }
}

Answer 1

Declare the JLabels:

//init
private JLabel quartersL, dimesL, nickelsL, penniesL;    

Replace the JLabels with the declared JLabels:

// 3. Add components to panel panel
quartersL = new JLabel("Quarters");
dimesL = new JLabel("Dimes");
nickelsL = new JLabel("Nickels");
penniesL = new JLabel("Pennies");

panel.add(new JLabel("Enter Change (1-99):"));
panel.add(changeTF);
panel.add(quartersL);
panel.add(new JTextField(quarters));
panel.add(dimesL);
panel.add(new JTextField(dimes));
panel.add(nickelsL);
panel.add(new JTextField(nickels));
panel.add(penniesL);
panel.add(new JTextField(pennies));
panel.add(calculateBtn);
//content.add(clearBtn);

Output the result into the JLabels:

public void actionPerformed(ActionEvent e)
    {
        String dyStr = changeTF.getText();
        change = Integer.parseInt(dyStr);
        while (change != 0)
        {
            while (change >= 25)
            { //Subtact & Count Quarters
                change = change - QUARTERS;
                quarters++;
            } //Subtract & Count Dimes
            while (change >= 10)
            {
                change = change - DIMES;
                dimes++;
            } //Subtract & Count Nickels
            while (change >= 5)
            {
                change = change - NICKELS;
                nickels++;
            }
            pennies = change;
        }

        // Update the JLabels to display the result
        quartersL.setText("" + quarters);
        dimesL.setText("" + dimes);
        nickelsL.setText("" + nickels);
        penniesL.setText("" + pennies);

    }

Answer 2

where do I need to place the calculations

Well, the ActionListener is the correct place

how to get the resulting variables to output

You need to make the JLabels you want to change into instance fields, like changeTF, then you can access them from your actionPerformed method, like you are the changeTF field