Many Java programs use tool tips in Java Swing to display more information when the mouse cursor hovers over a button or text field. There is a method of making text within that tool tip bold, italics, colored and more. Below is an illustration of the command that uses HTML tags to display that formatting in the ToolTip.
btnPortfolio.setToolTipText("<html>Select the Portfolio file <b>from JStock</b>. File name has to be <b>buyportfolio.csv</br></html>");