Java Swing on high-DPI screen

You could physically modify the look and feel's font settings...

import java.awt.EventQueue;
import java.awt.Font;
import java.util.Set;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                setDefaultSize(24);

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new JLabel("Happy as a pig in a blanket"));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public static void setDefaultSize(int size) {

        Set<Object> keySet = UIManager.getLookAndFeelDefaults().keySet();
        Object[] keys = keySet.toArray(new Object[keySet.size()]);

        for (Object key : keys) {

            if (key != null && key.toString().toLowerCase().contains("font")) {

                System.out.println(key);
                Font font = UIManager.getDefaults().getFont(key);
                if (font != null) {
                    font = font.deriveFont((float)size);
                    UIManager.put(key, font);
                }

            }

        }

    }

}

We use a similar approach to increase/decrease the font size of the running application to test layouts (and eventually allow the user some additional control over the font size)

I can't say for sure if this fully addresses the issue, but apparently high DPI Java is fixed for Mac in Java 7, and fixed for Linux and Windows in Java 9.

JEP 263: HiDPI Graphics on Windows and Linux: http://openjdk.java.net/jeps/263

corresponding ticket: https://bugs.openjdk.java.net/browse/JDK-8055212