Java Example

• components

  • components/AddButton.java

    package refactoring_guru.mediator.example.components;
    
    import refactoring_guru.mediator.example.mediator.Mediator;
    import refactoring_guru.mediator.example.mediator.Note;
    
    import javax.swing.*;
    import java.awt.event.ActionEvent;
    
    /**
     * Concrete components don't talk with each other. They have only one
    * communication channel–sending requests to the mediator.
    */
    public class AddButton extends JButton implements Component {
        private Mediator mediator;
    
        public AddButton() {
            super("Add");
        }
    
        @Override
        public void setMediator(Mediator mediator) {
            this.mediator = mediator;
        }
    
        @Override
        protected void fireActionPerformed(ActionEvent actionEvent) {
            mediator.addNewNote(new Note());
        }
    
        @Override
        public String getName() {
            return "AddButton";
        }
    }

  • components/Component.java

    package refactoring_guru.mediator.example.components;
    
    import refactoring_guru.mediator.example.mediator.Mediator;
    
    /**
     * Common component interface.
    */
    public interface Component {
        void setMediator(Mediator mediator);
        String getName();
    }

  • components/DeleteButton.java

    package refactoring_guru.mediator.example.components;
    
    import refactoring_guru.mediator.example.mediator.Mediator;
    
    import javax.swing.*;
    import java.awt.event.ActionEvent;
    
    /**
     * Concrete components don't talk with each other. They have only one
    * communication channel–sending requests to the mediator.
    */
    public class DeleteButton extends JButton  implements Component {
        private Mediator mediator;
    
        public DeleteButton() {
            super("Del");
        }
    
        @Override
        public void setMediator(Mediator mediator) {
            this.mediator = mediator;
        }
    
        @Override
        protected void fireActionPerformed(ActionEvent actionEvent) {
            mediator.deleteNote();
        }
    
        @Override
        public String getName() {
            return "DelButton";
        }
    }

  • components/Filter.java

    package refactoring_guru.mediator.example.components;
    
    import refactoring_guru.mediator.example.mediator.Mediator;
    import refactoring_guru.mediator.example.mediator.Note;
    
    import javax.swing.*;
    import java.awt.event.KeyEvent;
    import java.util.ArrayList;
    
    /**
     * Concrete components don't talk with each other. They have only one
    * communication channel–sending requests to the mediator.
    */
    public class Filter extends JTextField implements Component {
        private Mediator mediator;
        private ListModel listModel;
    
        public Filter() {}
    
        @Override
        public void setMediator(Mediator mediator) {
            this.mediator = mediator;
        }
    
        @Override
        protected void processComponentKeyEvent(KeyEvent keyEvent) {
            String start = getText();
            searchElements(start);
        }
    
        public void setList(ListModel listModel) {
            this.listModel = listModel;
        }
    
        private void searchElements(String s) {
            if (listModel == null) {
                return;
            }
    
            if (s.equals("")) {
                mediator.setElementsList(listModel);
                return;
            }
    
            ArrayList<Note> notes = new ArrayList<>();
            for (int i = 0; i < listModel.getSize(); i++) {
                notes.add((Note) listModel.getElementAt(i));
            }
            DefaultListModel<Note> listModel = new DefaultListModel<>();
            for (Note note : notes) {
                if (note.getName().contains(s)) {
                    listModel.addElement(note);
                }
            }
            mediator.setElementsList(listModel);
        }
    
        @Override
        public String getName() {
            return "Filter";
        }
    }

  • components/List.java

    
    import refactoring_guru.mediator.example.mediator.Mediator;
    import refactoring_guru.mediator.example.mediator.Note;
    
    import javax.swing.*;
    
    /**
     * Concrete components don't talk with each other. They have only one
    * communication channel–sending requests to the mediator.
    */
    @SuppressWarnings("unchecked")
    public class List extends JList implements Component {
        private Mediator mediator;
        private final DefaultListModel LIST_MODEL;
    
        public List(DefaultListModel listModel) {
            super(listModel);
            this.LIST_MODEL = listModel;
            setModel(listModel);
            this.setLayoutOrientation(JList.VERTICAL);
            Thread thread = new Thread(new Hide(this));
            thread.start();
        }
    
        @Override
        public void setMediator(Mediator mediator) {
            this.mediator = mediator;
        }
    
        public void addElement(Note note) {
            LIST_MODEL.addElement(note);
            int index = LIST_MODEL.size() - 1;
            setSelectedIndex(index);
            ensureIndexIsVisible(index);
            mediator.sendToFilter(LIST_MODEL);
        }
    
        public void deleteElement() {
            int index = this.getSelectedIndex();
            try {
                LIST_MODEL.remove(index);
                mediator.sendToFilter(LIST_MODEL);
            } catch (ArrayIndexOutOfBoundsException ignored) {}
        }
    
        public Note getCurrentElement() {
            return (Note)getSelectedValue();
        }
    
        @Override
        public String getName() {
            return "List";
        }
    
        private class Hide implements Runnable {
            private List list;
    
            Hide(List list) {
                this.list = list;
            }
    
            @Override
            public void run() {
                while (true) {
                    try {
                        Thread.sleep(300);
                    } catch (InterruptedException ex) {
                        ex.printStackTrace();
                    }
                    if (list.isSelectionEmpty()) {
                        mediator.hideElements(true);
                    } else {
                        mediator.hideElements(false);
                    }
                }
            }
        }
    }

  • components/SaveButton.java

    package refactoring_guru.mediator.example.components;
    
    import refactoring_guru.mediator.example.mediator.Mediator;
    
    import javax.swing.*;
    import java.awt.event.ActionEvent;
    
    /**
     * Concrete components don't talk with each other. They have only one
    * communication channel–sending requests to the mediator.
    */
    public class SaveButton extends JButton implements Component {
        private Mediator mediator;
    
        public SaveButton() {
            super("Save");
        }
    
        @Override
        public void setMediator(Mediator mediator) {
            this.mediator = mediator;
        }
    
        @Override
        protected void fireActionPerformed(ActionEvent actionEvent) {
            mediator.saveChanges();
        }
    
        @Override
        public String getName() {
            return "SaveButton";
        }
    }

  • components/TextBox.java

    package refactoring_guru.mediator.example.components;
    
    import refactoring_guru.mediator.example.mediator.Mediator;
    
    import javax.swing.*;
    import java.awt.event.KeyEvent;
    
    /**
     * Concrete components don't talk with each other. They have only one
    * communication channel–sending requests to the mediator.
    */
    public class TextBox extends JTextArea implements Component {
        private Mediator mediator;
    
        @Override
        public void setMediator(Mediator mediator) {
            this.mediator = mediator;
        }
    
        @Override
        protected void processComponentKeyEvent(KeyEvent keyEvent) {
            mediator.markNote();
        }
    
        @Override
        public String getName() {
            return "TextBox";
        }
    }

  • components/Title.java

    package refactoring_guru.mediator.example.components;
    
    import refactoring_guru.mediator.example.mediator.Mediator;
    
    import javax.swing.*;
    import java.awt.event.KeyEvent;
    
    /**
     * Concrete components don't talk with each other. They have only one
    * communication channel–sending requests to the mediator.
    */
    public class Title extends JTextField implements Component {
        private Mediator mediator;
    
        @Override
        public void setMediator(Mediator mediator) {
            this.mediator = mediator;
        }
    
        @Override
        protected void processComponentKeyEvent(KeyEvent keyEvent) {
            mediator.markNote();
        }
    
        @Override
        public String getName() {
            return "Title";
        }
    }

• mediator

  • mediator/Editor.java

    package refactoring_guru.mediator.example.mediator;
    
    import refactoring_guru.mediator.example.components.*;
    import refactoring_guru.mediator.example.components.Component;
    import refactoring_guru.mediator.example.components.List;
    
    import javax.swing.*;
    import javax.swing.border.LineBorder;
    import java.awt.*;
    
    /**
     * Concrete mediator. All chaotic communications between concrete components
    * have been extracted to the mediator. Now components only talk with the
    * mediator, which knows who has to handle a request.
    */
    public class Editor implements Mediator {
        private Title title;
        private TextBox textBox;
        private AddButton add;
        private DeleteButton del;
        private SaveButton save;
        private List list;
        private Filter filter;
    
        private JLabel titleLabel = new JLabel("Title:");
        private JLabel textLabel = new JLabel("Text:");
        private JLabel label = new JLabel("Add or select existing note to proceed...");
    
        /**
         * Here the registration of components by the mediator.
         */
        @Override
        public void registerComponent(Component component) {
            component.setMediator(this);
            switch (component.getName()) {
                case "AddButton":
                    add = (AddButton)component;
                    break;
                case "DelButton":
                    del = (DeleteButton)component;
                    break;
                case "Filter":
                    filter = (Filter)component;
                    break;
                case "List":
                    list = (List)component;
                    this.list.addListSelectionListener(listSelectionEvent -> {
                        Note note = (Note)list.getSelectedValue();
                        if (note != null) {
                            getInfoFromList(note);
                        } else {
                            clear();
                        }
                    });
                    break;
                case "SaveButton":
                    save = (SaveButton)component;
                    break;
                case "TextBox":
                    textBox = (TextBox)component;
                    break;
                case "Title":
                    title = (Title)component;
                    break;
            }
        }
    
        /**
         * Various methods to handle requests from particular components.
         */
        @Override
        public void addNewNote(Note note) {
            title.setText("");
            textBox.setText("");
            list.addElement(note);
        }
    
        @Override
        public void deleteNote() {
            list.deleteElement();
        }
    
        @Override
        public void getInfoFromList(Note note) {
            title.setText(note.getName().replace('*', ' '));
            textBox.setText(note.getText());
        }
    
        @Override
        public void saveChanges() {
            try {
                Note note = (Note) list.getSelectedValue();
                note.setName(title.getText());
                note.setText(textBox.getText());
                list.repaint();
            } catch (NullPointerException ignored) {}
        }
    
        @Override
        public void markNote() {
            try {
                Note note = list.getCurrentElement();
                String name = note.getName();
                if (!name.endsWith("*")) {
                    note.setName(note.getName() + "*");
                }
                list.repaint();
            } catch (NullPointerException ignored) {}
        }
    
        @Override
        public void clear() {
            title.setText("");
            textBox.setText("");
        }
    
        @Override
        public void sendToFilter(ListModel listModel) {
            filter.setList(listModel);
        }
    
        @SuppressWarnings("unchecked")
        @Override
        public void setElementsList(ListModel list) {
            this.list.setModel(list);
            this.list.repaint();
        }
    
        @Override
        public void hideElements(boolean flag) {
            titleLabel.setVisible(!flag);
            textLabel.setVisible(!flag);
            title.setVisible(!flag);
            textBox.setVisible(!flag);
            save.setVisible(!flag);
            label.setVisible(flag);
        }
    
        @Override
        public void createGUI() {
            JFrame notes = new JFrame("Notes");
            notes.setSize(960, 600);
            notes.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
            JPanel left = new JPanel();
            left.setBorder(new LineBorder(Color.BLACK));
            left.setSize(320, 600);
            left.setLayout(new BoxLayout(left, BoxLayout.Y_AXIS));
            JPanel filterPanel = new JPanel();
            filterPanel.add(new JLabel("Filter:"));
            filter.setColumns(20);
            filterPanel.add(filter);
            filterPanel.setPreferredSize(new Dimension(280, 40));
            JPanel listPanel = new JPanel();
            list.setFixedCellWidth(260);
            listPanel.setSize(320, 470);
            JScrollPane scrollPane = new JScrollPane(list);
            scrollPane.setPreferredSize(new Dimension(275, 410));
            listPanel.add(scrollPane);
            JPanel buttonPanel = new JPanel();
            add.setPreferredSize(new Dimension(85, 25));
            buttonPanel.add(add);
            del.setPreferredSize(new Dimension(85, 25));
            buttonPanel.add(del);
            buttonPanel.setLayout(new FlowLayout());
            left.add(filterPanel);
            left.add(listPanel);
            left.add(buttonPanel);
            JPanel right = new JPanel();
            right.setLayout(null);
            right.setSize(640, 600);
            right.setLocation(320, 0);
            right.setBorder(new LineBorder(Color.BLACK));
            titleLabel.setBounds(20, 4, 50, 20);
            title.setBounds(60, 5, 555, 20);
            textLabel.setBounds(20, 4, 50, 130);
            textBox.setBorder(new LineBorder(Color.DARK_GRAY));
            textBox.setBounds(20, 80, 595, 410);
            save.setBounds(270, 535, 80, 25);
            label.setFont(new Font("Verdana", Font.PLAIN, 22));
            label.setBounds(100, 240, 500, 100);
            right.add(label);
            right.add(titleLabel);
            right.add(title);
            right.add(textLabel);
            right.add(textBox);
            right.add(save);
            notes.setLayout(null);
            notes.getContentPane().add(left);
            notes.getContentPane().add(right);
            notes.setResizable(false);
            notes.setLocationRelativeTo(null);
            notes.setVisible(true);
        }
    }

  • mediator/Mediator.java

    package refactoring_guru.mediator.example.mediator;
    
    import refactoring_guru.mediator.example.components.Component;
    
    import javax.swing.*;
    
    /**
     * Common mediator interface.
    */
    public interface Mediator {
        void addNewNote(Note note);
        void deleteNote();
        void getInfoFromList(Note note);
        void saveChanges();
        void markNote();
        void clear();
        void sendToFilter(ListModel listModel);
        void setElementsList(ListModel list);
        void registerComponent(Component component);
        void hideElements(boolean flag);
        void createGUI();
    }

  • mediator/Note.java

    package refactoring_guru.mediator.example.mediator;
    
    /**
     * Note class.
    */
    public class Note {
        private String name;
        private String text;
    
        public Note() {
            name = "New note";
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public void setText(String text) {
            this.text = text;
        }
    
        public String getName() {
            return name;
        }
    
        public String getText() {
            return text;
        }
    
        @Override
        public String toString() {
            return name;
        }
    }

• Demo.java

package refactoring_guru.mediator.example;

import refactoring_guru.mediator.example.components.*;
import refactoring_guru.mediator.example.mediator.Editor;
import refactoring_guru.mediator.example.mediator.Mediator;

import javax.swing.*;

/**
 * Demo class. Everything comes together here.
 */
public class Demo {
    public static void main(String[] args) {
        Mediator mediator = new Editor();

        mediator.registerComponent(new Title());
        mediator.registerComponent(new TextBox());
        mediator.registerComponent(new AddButton());
        mediator.registerComponent(new DeleteButton());
        mediator.registerComponent(new SaveButton());
        mediator.registerComponent(new List(new DefaultListModel()));
        mediator.registerComponent(new Filter());

        mediator.createGUI();
    }
}