It is a regular JTree! —mostly. I am using a custom TreeCellRenderer, which uses a JPanel with some labels on top, and a JTextPane for to display the comment it

It is a regular JTree! —mostly. I am using a custom TreeCellRenderer, which uses a JPanel with some labels on top, and a JTextPane for to display the comment itself (since the HN API gives back comments as html, I use JTextPane to parse/render that html). Edit: it also may look different if you aren't used to seeing the 'Nimbus' Look and Feel—its JTree looks fairly different.