ADDITIONAL OS VERSION INFORMATION :
macOS 10.13.3

A DESCRIPTION OF THE PROBLEM :
Two apostrophe characters are entered in a text field instead of one with "U.S. International - PC" keyboard layout, if a user types one apostrophe character followed by one consonant Latin letter.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Go to "System Preferences -> Keyboard -> Input Sources" and add "U.S. International - PC".
2. Compile and run the test case, whose code is provided below.
3. Press apostrophe key " ' ", press any consonant Latin letter key, for example " d " key on a keyboard.

The bug is reproduced, if two apostrophe characters ('') are entered in the text field.

---------- BEGIN SOURCE ----------
import javax.swing.*;
  
public class JTextFieldTest {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new JTextField(20));
                frame.pack();
                frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
                frame.setVisible(true);
                frame.setLocationRelativeTo(null);
            }
        });
    }
}
---------- END SOURCE ----------