GUI.java

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.GregorianCalendar;
import java.util.Stack;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class GUI implements ActionListener{

    /* JFrame works like the main Windoow where components like lables, buttons ,textfields are added to create a GUI */
    /* Text Area */
    JFrame window;
    JTextArea textArea; //Multi-line area that displays plain text
    JScrollPane scrollPane; //Add Scrollbar when we enter beyound text area
    boolean wordWrapOn = false;

    /* Top Menu Bar */
    JMenuBar menuBar; //Add Menu bar of Notepad(File, Edit , Format , Colour etc)
    JMenu menuFile, menuEdit , menuFormat , menuColour; //Menu icons
    
    /* File Menu */
    JMenuItem iNew , iOpen , iSave , iSaveAs, iExit; //Menu Items 

    /* Format Menu */
    JMenuItem iWrap, iFontArial , iFontCSMS , iFontTNR , iFontSize8, iFontSize12 , iFontSize16 , iFontSize20 , iFontSize24 , iFontSize28;
    JMenu menuFont , menuFontSize;

    /* Edit Menu */
    JMenuItem iCopy ,iCopy1 , iCut1 , iCut , iPaste1 ,iPaste , iDelete , iTD, iAllSel ;
    Stack<String> stack = new Stack<>();
    String str = "";
    int i=0, pos = 0;
    GregorianCalendar gcalendar;

    /* Colour Menu */
    JMenuItem iCol1 , iCol2 , iCol3;

    File fun = new File(this);
    Format format = new Format(this);
    Edit edit = new Edit(this);
    Colour col = new Colour(this);

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

    }

    public GUI(){
        createWindow();
        createTextArea();
        createMenuBar();
        createFileMenu();
        createEdit();
        createFormatMenu();
        createColourMenu();

        format.selectedFont = "Arial";
        format.createFont(12);
        format.wordWrap();
        col.changeColour("White");
        window.setVisible(true); //We can see window
    }

    public void createWindow(){
        window = new JFrame("Notepad");
        window.setSize(800, 600);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //we need to close frame properly
    }

    public void createTextArea(){
        textArea = new JTextArea();
        scrollPane = new JScrollPane(textArea , JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED , JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        scrollPane.setBorder(BorderFactory.createEmptyBorder()); //Remove borders of Scroll Bar 
        window.add(scrollPane);
 
    }

    public void createMenuBar(){
        menuBar = new JMenuBar();
        window.setJMenuBar(menuBar);

        menuFile = new JMenu("File");
        menuBar.add(menuFile);
        
        menuEdit = new JMenu("Edit");
        menuBar.add(menuEdit);

        menuFormat = new JMenu("Format");
        menuBar.add(menuFormat);

        menuColour = new JMenu("Background Colour");
        menuBar.add(menuColour);
    }

    public void createFileMenu(){
        iNew = new JMenuItem("New");
        iNew.addActionListener(this); //we're implementing Action Listner to this GUI class
        iNew.setActionCommand("New"); //set string value to trigger the ActionListener on this item 
        menuFile.add(iNew);

        iOpen = new JMenuItem("Open");
        iOpen.addActionListener(this); 
        iOpen.setActionCommand("Open"); 
        menuFile.add(iOpen);

        iSave = new JMenuItem("Save");
        iSave.addActionListener(this); 
        iSave.setActionCommand("Save"); 
        menuFile.add(iSave);

        iSaveAs = new JMenuItem("Save As");
        iSaveAs.addActionListener(this); 
        iSaveAs.setActionCommand("SaveAs"); 
        menuFile.add(iSaveAs);

        iExit = new JMenuItem("Exit");
        iExit.addActionListener(this); 
        iExit.setActionCommand("Exit"); 
        menuFile.add(iExit);
    }

    public void createEdit(){
        iCopy = new JMenuItem("Copy to Stack");
        iCopy.addActionListener(this);
        iCopy.setActionCommand("Copy to Stack");
        menuEdit.add(iCopy);

        iCut = new JMenuItem("Cut to Stack");
        iCut.addActionListener(this);
        iCut.setActionCommand("Cut to Stack");
        menuEdit.add(iCut);

        iPaste = new JMenuItem("Paste from Stack");
        iPaste.addActionListener(this);
        iPaste.setActionCommand("Paste from Stack");
        menuEdit.add(iPaste);

        iCopy1 = new JMenuItem("Copy (Ctrl + C)");
        iCopy1.addActionListener(this);
        iCopy1.setActionCommand("Copy (Ctrl + C)");
        menuEdit.add(iCopy1);

        iCut1 = new JMenuItem("Cut (Ctrl + X)");
        iCut1.addActionListener(this);
        iCut1.setActionCommand("Cut (Ctrl + X)");
        menuEdit.add(iCut1);

        iPaste1 = new JMenuItem("Paste (Ctrl + V)");
        iPaste1.addActionListener(this);
        iPaste1.setActionCommand("Paste (Ctrl + V)");
        menuEdit.add(iPaste1);

        iTD = new JMenuItem("Time & Date");
        iTD.addActionListener(this);
        iTD.setActionCommand("Time & Date");
        menuEdit.add(iTD);
    }

    public void createFormatMenu(){

        iWrap = new JMenuItem("Word Wrap : OFF");
        iWrap.addActionListener(this);
        iWrap.setActionCommand("Word Wrap");
        menuFormat.add(iWrap);

        menuFont = new JMenu("Font");
        menuFormat.add(menuFont);

        iFontArial = new JMenuItem("Arial");
        iFontArial.addActionListener(this);
        iFontArial.setActionCommand("Arial");
        menuFont.add(iFontArial);

        
        iFontCSMS = new JMenuItem("Comic Sans MS");
        iFontCSMS.addActionListener(this);
        iFontCSMS.setActionCommand("Comic Sans MS");
        menuFont.add(iFontCSMS);

        iFontTNR = new JMenuItem("Times New Roman");
        iFontTNR.addActionListener(this);
        iFontTNR.setActionCommand("Times New Roman");
        menuFont.add(iFontTNR);

        menuFontSize = new JMenu("Font Size");
        menuFormat.add(menuFontSize);

        iFontSize8 = new JMenuItem("8");
        iFontSize8.addActionListener(this);
        iFontSize8.setActionCommand("size8");
        menuFontSize.add(iFontSize8);

        iFontSize12 = new JMenuItem("12");
        iFontSize12.addActionListener(this);
        iFontSize12.setActionCommand("size12");
        menuFontSize.add(iFontSize12);

        iFontSize16 = new JMenuItem("16");
        iFontSize16.addActionListener(this);
        iFontSize16.setActionCommand("size16");
        menuFontSize.add(iFontSize16);

        iFontSize20 = new JMenuItem("20");
        iFontSize20.addActionListener(this);
        iFontSize20.setActionCommand("size20");
        menuFontSize.add(iFontSize20);

        iFontSize24 = new JMenuItem("24");
        iFontSize24.addActionListener(this);
        iFontSize24.setActionCommand("size24");
        menuFontSize.add(iFontSize24);

        iFontSize28 = new JMenuItem("28");
        iFontSize28.addActionListener(this);
        iFontSize28.setActionCommand("size28");
        menuFontSize.add(iFontSize28);
    }

    public void createColourMenu(){
        iCol1 = new JMenuItem("White");
        iCol1.addActionListener(this);
        iCol1.setActionCommand("White");
        menuColour.add(iCol1);

        iCol2 = new JMenuItem("Black");
        iCol2.addActionListener(this);
        iCol2.setActionCommand("Black");
        menuColour.add(iCol2);

        iCol3 = new JMenuItem("Blue");
        iCol3.addActionListener(this);
        iCol3.setActionCommand("Blue");
        menuColour.add(iCol3);
    }

    @Override
    public void actionPerformed(ActionEvent e){
        String command = e.getActionCommand();

        switch(command){
            case "New"          : fun.newFile();
                                    break;
            case "Open"         : fun.open();
                                    break;
            case "SaveAs"       : fun.saveAs();
                                    break;
            case "Save"         : fun.save();
                                    break;
            case "Exit"         : fun.exit();
                                    break; 
            case "Word Wrap"    : format.wordWrap();
                                    break;
            case "Arial"        : format.setFont(command);
                                    break;
            case "Comic Sans MS": format.setFont(command);
                                    break;
            case "Times New Roman": format.setFont(command);
                                    break;                                                
            case "size8"        : format.createFont(8);
                                    break;
            case "size12"        : format.createFont(12);
                                    break;
            case "size16"        : format.createFont(16);
                                    break;
            case "size20"        : format.createFont(20);
                                    break;
            case "size24"        : format.createFont(24);
                                    break; 
            case "size28"        : format.createFont(28);
                                    break;  
            case "White"         : col.changeColour(command); 
                                    break;  
            case "Black"         : col.changeColour(command); 
                                    break; 
            case "Blue"          : col.changeColour(command); 
                                    break;
            case "Copy to Stack" :  edit.editText(command);
                                    break;
            case "Copy (Ctrl + C)" :  edit.editText(command);
                                    break;
            case "Cut to Stack" :  edit.editText(command); 
                                    break; 
            case "Cut (Ctrl + X)" :  edit.editText(command);
                                    break;
            case "Paste from Stack" :  edit.editText(command); 
                                    break;
            case "Paste (Ctrl + V)" :  edit.editText(command);
                                    break;  
            case "Time & Date"   : edit.editText(command);
                                    break;                                     
        }
    }
}