Java JLabel, Why does "<html>/* test */</html>" result in the JLabel being empty?

I have a JLabel I'm populating it like this

String descriptionText = StringEscapeUtils.escapeHtml(rule.getDescription());
descriptionText = descriptionText.replaceAll("\n", "<br>");
descriptionLbl.setText(String.format("<html>%s</html>", descriptionText));

In this case, if rule.getDescription() returns something like "/* test */" the end result is an empty JLabel? Why is this? I thought that StringEscapeUtils#escapeHtml would have caught all the escape characters.

Solution

Here's a smaller test app that shows the problem:

import javax.swing.JFrame;
import javax.swing.JLabel;

public class LabelTest {

    public static void main(String args[]) {
        JFrame frame = new JFrame("Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JLabel label = new JLabel();

        String text = "<html>/test</html>";

        label.setText(text);

        frame.add(label);

        frame.setSize(500, 500);
        frame.setVisible(true);
    }
}

The only fix I've found is to use the special html code instead:

String text = "<html>&#47;test</html>";

You could have a processing method that uses replaceAll() to automate this process.

I'm not sure why this happens, and it doesn't seem to happen with any other special character. Weird.