久しぶりのプログラミング

SwingとImageIOを使ってファイル選択ダイアログで指定した画像を読み込み、その画像を画面内に4つ表示するプログラムを作ってみました。印刷機能も付けてみました。コメントが一切ありませんが…！
そういえばImageIO#readって対応してないファイルに対して例外がでるんじゃなくてnullが返ってくるのね…。そこらへんも考えてプログラムを作っていかねば

import javax.swing.JFrame;
import javax.swing.JComponent;
import javax.swing.JOptionPane;
import javax.swing.JFileChooser;
import javax.swing.SwingUtilities;

import javax.swing.filechooser.FileNameExtensionFilter;

import javax.swing.JMenu;
import javax.swing.JMenuItem;
import javax.swing.JMenuBar;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Dimension;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;

import java.awt.print.PageFormat;
import java.awt.print.Printable;
import java.awt.print.PrinterJob;
import java.awt.print.PrinterException;

import java.util.Optional;

import java.io.File;
import java.io.IOException;

public class Test extends JComponent{
    private Optional<BufferedImage> editImage = Optional.empty();
    
    public static void main(String... args){
        SwingUtilities.invokeLater(Test::start);
    }

    private static void start(){
        var test = new Test();
        var frame = new JFrame();
        
        test.setPreferredSize(new Dimension(600, 500));
        frame.setJMenuBar(Test.createMenuBar(test));
        frame.add(test);
        
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        frame.pack();
    }
    
    @Override
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        
        drawImage4(g, 0, 0, getWidth(), getHeight());
    }
    
    private void draw(Graphics g, int x, int y, int width, int height){
        g.setColor(Color.WHITE);
        g.fillRect(x, y, width, height);
        
        editImage.ifPresent(image -> {
            double ratio = Test.getRatio(width, height, image);
            int newWidth = (int)(image.getWidth() * ratio);
            int newHeight = (int)(image.getHeight() * ratio);

            g.drawImage(image, x, y, newWidth, newHeight, this);
        });
    }
    
    private void drawImage4(Graphics g, int x, int y, int width, int height){
        int halfWidth = width / 2;
        int halfHeight = height / 2;

        draw(g, x, y, halfWidth, halfHeight);
        draw(g, x + halfWidth, y, halfWidth, halfHeight);
        draw(g, x, y + halfHeight, halfWidth, halfHeight);
        draw(g, x + halfWidth, y + halfHeight, halfWidth, halfHeight);
    }
    
    private static JMenuBar createMenuBar(Test test){
        var menubar = new JMenuBar();
        var fileMenu = new JMenu("File");
        var openItem = new JMenuItem("Open");
        openItem.setMnemonic('O');
        
        openItem.addActionListener(e -> {
            Test.openLoadDialog(test);
        });
        
        var printItem = new JMenuItem("Print");
        printItem.setMnemonic('P');
        
        printItem.addActionListener(e -> {
            Test.printImage(test);
        });
        
        fileMenu.setMnemonic('F');
        fileMenu.add(openItem);
        fileMenu.add(printItem);
        
        menubar.add(fileMenu);
        
        return menubar;
    }
    
    private static void openLoadDialog(Test test){
        var chooser = new JFileChooser();
        chooser.setCurrentDirectory(new File("./"));
        chooser.setFileFilter(new FileNameExtensionFilter("Images", "jpg", "gif", "png"));
        
        if(chooser.showOpenDialog(test) == JFileChooser.APPROVE_OPTION){
            var file = chooser.getSelectedFile();
            test.load(file);
            test.repaint();
        }
    }
    
    private static void printImage(Test test){
        var job = PrinterJob.getPrinterJob();
            
        job.setPrintable((g, format, index) -> {
            if(index > 0){
                return Printable.NO_SUCH_PAGE;
            }

            test.drawImage4(g, 0, 0, (int)format.getImageableWidth(), (int)format.getImageableHeight());
                
            return Printable.PAGE_EXISTS;
        });
        
        if(job.printDialog()){
            try{
                job.print();
            }catch(PrinterException e){
                JOptionPane.showMessageDialog(test, "印刷に失敗しました: " + e.getMessage());
            }
        }
    }
    
    private void load(File file){
        try{
            editImage = Optional.ofNullable(ImageIO.read(file));
        }catch(IOException e){
            JOptionPane.showMessageDialog(this, "ファイルの読み込みに失敗しました");
        }
    }
    
    private static double getRatio(int width, int height, BufferedImage image){
        double widthRatio = (double)width / image.getWidth();
        double heightRatio = (double)height / image.getHeight();
        
        return Math.min(widthRatio, heightRatio);
    }
}