I have a table where each row represents a picture. In the column Path I store its absolute path. The string being kinda long, I would like that when I hover the mouse over
You say you store an absolute path in a cell. You are probably using a JLabel for setting absolute path string. Suppose you have a label in your cell, use html tags for expressing tooltip content:
JLabel label = new JLabel("Bla bla");
label.setToolTipText("information about cell
");
setToolTipText() can be used for some other Swing components if you are using something other than JLabel.