Flipping the cards for memory card game isn't working in java (without applets)

Question

I'm making a memory card game. I started by adding 5 ImageIcons with initial value(images) of the card in flipped state, added a button for flipping the cards through Action Listener but can't seem to get it flipped when I click the button. I'm still a beginner to GUI and I don't want to use applets.

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

//this class gonna control the basic ops of the game
public class MemoControl extends JFrame{

    public JLabel label;
    public JButton button;

            //images
            public ImageIcon image1;
            public JLabel label1;
            public ImageIcon image2;
            public JLabel label2;
            public ImageIcon image3;
            public JLabel label3;
            public ImageIcon image4;
            public JLabel label4;
            public ImageIcon image5;
            public JLabel label5;

            public MemoControl(){

                    setLayout(new FlowLayout());

                    image1 = new      ImageIcon(getClass().getResource("card_cover1.jpg"));
                    label1 = new JLabel(image1);
                    add(label1);

                    image2 = new ImageIcon(getClass().getResource("card_cover1.jpg"));
                    label2 = new JLabel(image2);
                    add(label2);

                    image3 = new ImageIcon(getClass().getResource("card_cover1.jpg"));
                    label3 = new JLabel(image3);
                    add(label3);

                    image4 = new ImageIcon(getClass().getResource("card_cover1.jpg"));
                    label4 = new JLabel(image4);
                    add(label4);

                    image5 = new ImageIcon(getClass().getResource("card_cover1.jpg"));
                    label5 = new JLabel(image5);
                    add(label5);


                    /*label = new JLabel("Welcome to AMY Memo Game");
                    add(label);*/

                    /*textField = new JTextField(15);
                    add(textField);*/

                    button = new JButton("Flip");
                    add(button);

                    EventClass event = new EventClass();
                    button.addActionListener(event);

                }//MyMemo constr end

                private class EventClass implements ActionListener{

                        public void actionPerformed(ActionEvent e){
                            if(e.getSource() == button){
                                image1 = new ImageIcon(getClass().getResource("deer_card.jpg"));
                                label1 = new JLabel(image1);}

                            }
                    }//Event class end

            public static void main(String args[]){

                    MemoControl gui = new MemoControl();

                    gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    gui.pack();
                    gui.setVisible(true);
                    gui.setTitle("My Memo");

            }//main end

    }//AMYMemo class end

The updated code:

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

//this class gonna control the basic ops of the game
public class MemoControl extends JFrame{

    public JLabel label;
    public JButton button;

            //images
            public ImageIcon image1;
            public JLabel label1;
            public ImageIcon image2;
            public JLabel label2;
            public ImageIcon image3;
            public JLabel label3;
            public ImageIcon image4;
            public JLabel label4;
            public ImageIcon image5;
            public JLabel label5;

            public MemoControl(){

                    setLayout(new FlowLayout());

                    image1 = new ImageIcon(getClass().getResource("card_cover1.jpg"));
                    label1 = new JLabel(image1);
                    add(label1);

                    image2 = new ImageIcon(getClass().getResource("card_cover1.jpg"));
                    label2 = new JLabel(image2);
                    add(label2);

                    image3 = new ImageIcon(getClass().getResource("card_cover1.jpg"));
                    label3 = new JLabel(image3);
                    add(label3);

                    image4 = new ImageIcon(getClass().getResource("card_cover1.jpg"));
                    label4 = new JLabel(image4);
                    add(label4);

                    image5 = new ImageIcon(getClass().getResource("card_cover1.jpg"));
                    label5 = new JLabel(image5);
                    add(label5);


                    /*label = new JLabel("Welcome to AMY Memo Game");
                    add(label);*/

                    /*textField = new JTextField(15);
                    add(textField);*/

                    button = new JButton("Flip");
                    add(button);

                    EventClass event = new EventClass();
                    button.addActionListener(event);

                }//MyMemo constr end

                private class EventClass implements ActionListener{

                        public void actionPerformed(ActionEvent e){
                            if(e.getSource() == button){

                                image1 = new ImageIcon(getClass().getResource("deer_card.jpg"));
                                label1.setIcon(image1);
                                }

                            }
                    }//Event class end

            public static void main(String args[]){

                    MemoControl gui = new MemoControl();

                    gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    gui.pack();
                    gui.setVisible(true);
                    gui.setTitle("My Memo");

            }//main end

    }//AMYMemo class end

Answer 1

Try label1.setIcon(image1); instead of label1 = new JLabel(image1); in EventClass. Because you create a new instance of JLabel with new Icon which is not added to your JFrame.

Answer 2

Expanding on @alex2410's answer,

In java you need to understand the difference between a variable, a reference, and an object.

label1 is a variable. It's a variable that can hold a reference to a "JLabel". new JLabel(..) creates an object and returns a reference to it.

so:

label1 = new JLabel() assigns a reference to newly created JLabel to label1.

When you add(label1) the value of label1 is passed to add. The value is a reference to the JLabel that you created earlier.

When you assign a reference of a new object to label1 after this, it doesn't change the object that was originally passed into add. Thus your screen will not change.

When you call label1.setIcon(...) you make a change to the object that label1 is pointing to. This object happens to be the same one that you added to the JFrame, so changing that object, will make a change to the screen.