Every time JTextPane.setText(...)
is called a new content type is determined. Start the text with "<html>"
and you’ve got HTML.
A new document is created, in your case HTMLDocument.
@mKorbel: the following creates every time HTML for the JTextPane.
buildSomething.append("<html>");
buildSomething1.append("<html>");
for (int i = 0; i < 10; i++) {
buildSomething.append("<span style=\"color:red\">" + myBirthday + "</span>");
buildSomething1.append("<b style=\"color:blue\">" + myBirthday + "</b>");
}