Story of making a task management application with swing, java

Hello, this is a certain company engineer. I'm studying because I think it's bad that I can only understand object-oriented programming vaguely even though I'm an engineer. As part of that, I decided to understand object-oriented writing while creating a task management app. I will leave the process as a memorandum.

For the time being, the specifications are like this. -Personal desktop application (I don't want to log in or anything else) ・ The basic UI respects trello https://trello.com/ -Use SQLite to record registered tasks

So I made the top page.

It works with a code like this. (Before refactoring.)

public class Top extends JFrame{
        /**
        *Launch application
        */
        public static void main(String[] args) {
        	Top frame = new Top("Task Manager");
            frame.setVisible(true);
        }
        
        Top(String title){
        	setTitle(title);
            setBounds(100, 100, 1000, 800);
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            setLayout(new FlowLayout());

            //TODO task display area
            //Task display area layout
            JPanel TodoPanel = new JPanel();
            TodoPanel.setPreferredSize(new Dimension(300, 600));
            TodoPanel.setBackground(Color.WHITE);
            TodoPanel.setLayout(new BoxLayout(TodoPanel, BoxLayout.X_AXIS));
            
            //Panel for placing titles
            JPanel TodoTitlePanel = new JPanel();
            TodoTitlePanel.setPreferredSize(new Dimension(300, 60));
            TodoTitlePanel.setBackground(Color.WHITE);
            TodoTitlePanel.setLayout(new BoxLayout(TodoTitlePanel, BoxLayout.Y_AXIS));
            TodoTitlePanel.setAlignmentY(0.0f);
            TodoPanel.add(TodoTitlePanel);
            
            //Title placement
            JLabel label = new JLabel("TODO");
            label.setFont(new Font("MS gothic", Font.BOLD, 32));
            label.setAlignmentX(0.5f);
            TodoTitlePanel.add(label);
            
            //Frame border
            LineBorder border = new LineBorder(Color.BLACK, 2, true);
            TodoPanel.setBorder(border);
            
            //DOING task display area
            //Task display area layout
            JPanel DoingPanel = new JPanel();
            DoingPanel.setPreferredSize(new Dimension(300, 600));
            DoingPanel.setBackground(Color.WHITE);
            DoingPanel.setLayout(new BoxLayout(DoingPanel, BoxLayout.X_AXIS));
            
            //Panel for placing titles
            JPanel DoingTitlePanel = new JPanel();
            DoingTitlePanel.setPreferredSize(new Dimension(300, 60));
            DoingTitlePanel.setBackground(Color.WHITE);
            DoingTitlePanel.setLayout(new BoxLayout(DoingTitlePanel, BoxLayout.Y_AXIS));
            DoingTitlePanel.setAlignmentY(0.0f);
            DoingPanel.add(DoingTitlePanel);
            
            //Title placement
            JLabel doingLabel = new JLabel("DOING");
            doingLabel.setFont(new Font("MS gothic", Font.BOLD, 32));
            doingLabel.setAlignmentX(0.5f);
            DoingTitlePanel.add(doingLabel);
            
            //Frame border
            LineBorder border2 = new LineBorder(Color.BLACK, 2, true);
            DoingPanel.setBorder(border2);
            
            //DONE task display area
            //Task display area layout
            JPanel DonePanel = new JPanel();
            DonePanel.setPreferredSize(new Dimension(300, 600));
            DonePanel.setBackground(Color.WHITE);
            DonePanel.setLayout(new BoxLayout(DonePanel, BoxLayout.X_AXIS));
            
            //Panel for placing titles
            JPanel DoneTitlePanel = new JPanel();
            DoneTitlePanel.setPreferredSize(new Dimension(300, 60));
            DoneTitlePanel.setBackground(Color.WHITE);
            DoneTitlePanel.setLayout(new BoxLayout(DoneTitlePanel, BoxLayout.Y_AXIS));
            DoneTitlePanel.setAlignmentY(0.0f);
            DonePanel.add(DoneTitlePanel);
            
            //Frame border
            LineBorder border3 = new LineBorder(Color.BLACK, 2, true);
            DonePanel.setBorder(border3);
            
            //Title placement
            JLabel doneLabel = new JLabel("DONE");
            doneLabel.setFont(new Font("MS gothic", Font.BOLD, 32));
            doneLabel.setAlignmentX(0.5f);
            DoneTitlePanel.add(doneLabel);
            
            //Button layout
            JPanel buttonPanel = new JPanel();
            
            JButton createButton = new JButton("Create New");
            createButton.setPreferredSize(new Dimension(100,50));
            buttonPanel.add(createButton);
            
            JButton editButton = new JButton("Edit task");
            editButton.setPreferredSize(new Dimension(100,50));
            buttonPanel.add(editButton);

            Container contentPane = getContentPane();
            contentPane.add(TodoPanel);
            contentPane.add(DoingPanel);
            contentPane.add(DonePanel);
            contentPane.add(buttonPanel);
          }
} 

It's long. There are three places where the same processing is done. When making labels and panels with swing, it is troublesome because you have to new each time. So, the code below summarizes the duplicated processing.

public class Top extends JFrame{
        /**
        *Launch application
        */
        public static void main(String[] args) {
        	Top frame = new Top("Task Manager");
            frame.setVisible(true);
        }
        
        Top(String title){
        	setTitle(title);
            setBounds(100, 100, 1000, 800);
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            setLayout(new FlowLayout());

            //TODO task display
            makeTaskPanel("TODO");
            
            //DOING task display
            makeTaskPanel("DOING");
            
            //DONE task display area
            makeTaskPanel("DONE");
            
            //Button layout
            JPanel buttonPanel = new JPanel();
            TaskRegister taskRegisterPanel = new TaskRegister();
            this.add(taskRegisterPanel);
            taskRegisterPanel.setVisible(false);
            JButton createButton = new JButton("Create New");
            
            buttonPanel.add(createButton);
            
            JButton editButton = new JButton("Edit task");
            editButton.setPreferredSize(new Dimension(100,50));
            buttonPanel.add(editButton);

            Container contentPane = getContentPane();
            contentPane.add(buttonPanel);
          }
        
        public void makeTaskPanel(String panelTitle){
        	//Create a task panel with the title text specified in title
            JPanel mainPanel = new JPanel();
            JPanel titlePanel = new JPanel();
            JLabel titleLabel = new JLabel(panelTitle);
            LineBorder border = new LineBorder(Color.BLACK, 2, true);
            
        	//Task display area layout
            mainPanel.setPreferredSize(new Dimension(300, 600));
            mainPanel.setBackground(Color.WHITE);
            mainPanel.setLayout(new BoxLayout(mainPanel, BoxLayout.X_AXIS));
            
            //Panel for placing titles
            titlePanel.setPreferredSize(new Dimension(300, 60));
            titlePanel.setBackground(Color.WHITE);
            titlePanel.setLayout(new BoxLayout(titlePanel, BoxLayout.Y_AXIS));
            titlePanel.setAlignmentY(0.0f);
            mainPanel.add(titlePanel);
            
            //Title placement
            titleLabel.setFont(new Font("MS gothic", Font.BOLD, 32));
            titleLabel.setAlignmentX(0.5f);
            titlePanel.add(titleLabel);
            
            //Frame border
            mainPanel.setBorder(border);
            
            Container contentPane = getContentPane();
            contentPane.add(mainPanel);
        }
} 

What was duplicated

1. New necessary panel, label, etc.
2. Arrange by playing around with the size Since it was a part to do, I cut out that part into a method. In object-oriented programming, cohesion is strong and coupling is low </ strong>, the better the design.