Demo of MVC concepts using Java's Swing.

Swing_MVC_MultiCounterDemo.java

import javax.swing.*;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;
import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class Swing_MVC_MultiCounterDemo extends JFrame {

    // See also two inner classes: CounterWidget & CounterModel

    final CounterModel model;

    public Swing_MVC_MultiCounterDemo() {{
        setTitle("Counter MVC demo using Swing");
        model = new CounterModel(0);
        add(new JPanel(){{
            setBorder(BorderFactory.createTitledBorder("Single Shared Model"));
            add(new CounterWidget(model).view);
            add(new CounterWidget(model).view);
            setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
        }});
        add(new JPanel(){{
            setBorder(BorderFactory.createTitledBorder("Two Separate Models"));
            add(new CounterWidget(new CounterModel(3)).view);
            add(new CounterWidget(new CounterModel(17)).view);
            setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
        }});
        getContentPane().setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS));
        pack();
        setLocation(500, 500);
    }}

    public static void main(String[] args) {
        Swing_MVC_MultiCounterDemo demo = new Swing_MVC_MultiCounterDemo();
        demo.addWindowListener(new WindowAdapter()
        {
            @Override
            public void windowClosing(WindowEvent e)
            {
                e.getWindow().dispose();
                System.out.println("Frame closed, views/controllers eligible for GC, model value = "
                        + demo.model.getCount() + ". Now exit."); ;
            }
        });
        demo.setVisible(true);
    }

    public class CounterWidget {

        final View view;

        class View extends JPanel {
            final JTextField text;
            final JButton plus;
            final JButton minus;
            View(CounterModel model) {{
                add(new JLabel("Count:"));
                text = new JTextField("0", 4);
                text.setDocument(model);
                add(text);
                plus = new JButton("+");
                final int s = (int) (getFont().getSize() * 1.7);
                plus.setPreferredSize(new Dimension(s, s));
                add(plus);
                minus = new JButton("-");
                minus.setPreferredSize(new Dimension(s, s));
                add(minus);
            }}
        }

        CounterWidget(CounterModel model) {
            view = new View(model);
            // controller logic
            view.plus.addActionListener(e -> {
                model.increment();
            });
            view.minus.addActionListener(e -> {
                model.decrement();
            });
        }
    }

    public class CounterModel extends PlainDocument {
        CounterModel(int initialValue) {
            setCount(initialValue);
        }
        void increment() {
            setCount(getCount() + 1);
        }
        void decrement() {
            setCount(getCount() - 1);
        }
        private void setCount(int i) {
            try {
                super.remove(0, getLength());
                super.insertString(0, "" + i, null);
            } catch (BadLocationException e) {
                throw new UnsupportedOperationException(e);
            }
        }

        int getCount() {
            try {
                return Integer.parseInt(super.getText(0, super.getLength()));
            } catch (BadLocationException e) {
                throw new UnsupportedOperationException(e);
            }
        }

        public void insertString(int offset, String str, AttributeSet attr) throws BadLocationException {
            for (int i = 0; i < str.length(); i++) {
                final char c = str.charAt(i);
                if (!"0123456789".contains(String.valueOf(c)))
                    if (i == 0 && c != '-') {
                        return;
                    }
            }
            super.insertString(offset, str, attr);
        }
    }
}

That app, when running, looks like:

The first two counters move up and down together. The third and fourth two are independent of each other (as well as independent to the first two).