How do I update a JLabel during run time

Question

the JLabel's name is set to an int which changes as the user modifies the number, i tried label.revalidate and Label.repaint after the user changes the int value. i have seen in similar questions people suggest creating a new jlabel everytime, but im wondering if there is a simpler way? the code is very long so i will summerize when needed.

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class officia {
    static JFrame Frame;
    static JPanel Panel;
    static JTextField healthPlace;
    static String health="0";
    static JButton begin;
    static JLabel heart;
    static int loop;
    
    public static void main(String[] args) {
    
    Panel = new JPanel();
    
    Frame = new JFrame();
    Frame.setSize(500,1000);
    Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Frame.add(Panel);
    Panel.setLayout(null);
    //adds panel and frame
    
    healthPlace = new JTextField();
    healthPlace.setBounds(170, 130, 165, 25);
    Panel.add(healthPlace);
    
    begin = new JButton("Begin");
    begin.setBounds(217, 185, 70, 25);
    Panel.add(begin);
    
    while(loop==1)
    loop=0;
        
    heart = new JLabel(health);
    heart.setBounds(150, -85, 500, 500);
    Panel.add(heart);
    
    Frame.setVisible(true); 
    //inputs gui's
    
    
    ActionListener beginPressed = new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
    
            health = healthPlace.getText();
            loop=1;
    }
};
begin.addActionListener(beginPressed);
}
}

Answer 1

You're working in a event driven environment, that is, something happens and you respond to it.

This means, you're while-loop is ill-conceived and is probably the source of your issue. How can the ActionListener for the button be added when the loop is running, but you seem to using the ActionListener to exit the loop...

I modified you code slightly, so when you press the button, it will update the label.

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class officia {

    static JFrame Frame;
    static JPanel Panel;
    static JTextField healthPlace;
    static String health = "0";
    static JButton begin;
    static JLabel heart;
    static int loop;

    public static void main(String[] args) {

        Panel = new JPanel();

        Frame = new JFrame();
        Frame.setSize(500, 1000);
        Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Frame.add(Panel);
        Panel.setLayout(null);
        //adds panel and frame  

        healthPlace = new JTextField();
        healthPlace.setBounds(170, 130, 165, 25);
        Panel.add(healthPlace);

        begin = new JButton("Begin");
        begin.setBounds(217, 185, 70, 25);
        Panel.add(begin);

        // This is ... interesting, but a bad idea
//        while (loop == 1) {
//            loop = 0;
//        }


        heart = new JLabel(health);
        heart.setBounds(150, -85, 500, 500);
        Panel.add(heart);

        Frame.setVisible(true);
        //inputs gui's

        ActionListener beginPressed = new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {

                health = healthPlace.getText();
                loop ++;
                heart.setText(Integer.toString(loop));
            }
        };
        begin.addActionListener(beginPressed);
    }
}

JLabel#setText is what's known as a stateful property, that is, it will trigger an update that will cause it to be painted, so, if it's not updating, you're doing something wrong.

Possible runnable example (of what I think you want to do)

You're working a very rich UI framework. One if it's, many, features, is the layout management framework, something you should seriously take the time to learn to understand and use.

See Laying Out Components Within a Container for more details.

Below is a relatively simple example which shows one way you might "swicth" between views based on a response to a user input

import java.awt.CardLayout;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new BasePane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class BasePane extends JPanel {

        private CardLayout cardLayout;

        public BasePane() {
            cardLayout = new CardLayout();
            setLayout(cardLayout);

            StartPane startPane = new StartPane(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    cardLayout.show(BasePane.this, "HeartPane");
                }
            });

            HeartPane heartPane = new HeartPane();

            add(startPane, "StartPane");
            add(heartPane, "HeartPane");
        }        
    }

    public class StartPane extends JPanel {

        public StartPane(ActionListener actionListener) {
            setBorder(new EmptyBorder(10, 10, 10, 10));
            setLayout(new GridBagLayout());
            JButton start = new JButton("Begin");
            add(start);

            start.addActionListener(actionListener);
        }

    }

    public class HeartPane extends JPanel {

        private JTextField heartTextField;
        private JLabel heartLabel;

        public HeartPane() {
            setBorder(new EmptyBorder(10, 10, 10, 10));
            setLayout(new GridBagLayout());
            heartLabel = new JLabel("Heart");
            heartTextField = new JTextField(10);

            add(heartLabel);
            add(heartTextField);
        }

    }
}