Rendering of a string can produce unexpected results on macOS (first character not rendering) if the string contains a surrogate pair. To reproduce the issue, run the following sample program:

import javax.swing.*;
import java.awt.*;

public class DrawTextTest {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame f = new JFrame();
            f.add(new MyComponent());
            f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
            f.setSize(150, 100);
            f.setLocationRelativeTo(null);
            f.setVisible(true);
        });
    }

    private static class MyComponent extends JComponent {
        @Override
        protected void paintComponent(Graphics g) {
            g.drawString("Hello", 50, 30);
            g.drawString("Hello" + new String(Character.toChars(0x1D400)), 50, 60);
        }
    }
}

It’s expected to see the word ‘Hello’ rendered correctly on both lines. Instead, on the second line, a box is rendered in place of ‘H’ letter (see attached image, obtained by running the program using build 9-ea+156).

The issue can be reproduced with latest Java 8 (8u121) and 9 (9-ea+156) builds.