This week's book giveaway is in the General Computing forum. We're giving away four copies of Arduino in Action and have Martin Evans, Joshua Noble, and Jordan Hochenbaum on-line! See this thread for details.
JTextField does not support styled content. The 'setDocument' method is used mainly for extensions of PlainDocument designed for input constraint (like the newer DocumentFilter) as shown in the api. JTextPane is the minimum choice for text styling.