JTextfield display a squarebox at the end of string in ar locale

run following test csse in ar locale, a squarebox is displayed at the end
of text. (the original test case FontTest.java is attached to reproduce the
problem in iw locale)

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

public class Test3 extends JFrame {
    private static String testString = Locale.getDefault().getDisplayLanguage();
    Test3() {
       super("Test3");
       JTextField jtf = new JTextField(testString);

       Container container = getContentPane();
       container.setLayout(new BorderLayout());
       container.add(jtf, BorderLayout.CENTER);
       setSize(getPreferredSize());
       pack();
       setVisible(true);
    }

    public static void main(String[] args) {
System.err.println("Locale: " + Locale.getDefault().toString());
System.err.println("file.encoding: " + System.getProperty("file.encoding"));
       Test3 test3 = new Test3();
    }
}