Difficulties understanding the renderers mechanism of swing's JTable and JTree

Question

Often, when using JTable or JTree user writes and assign it is own specific cell renderer.

It is very common to inherit user\'s component

Answer 1

It's an implementation of the flyweight pattern.

When the JTable repaints itself, it starts a loop and iterates over every cell that must be painted.

For each cell, it invokes the renderer with the arguments corresponding to the cell. The renderer returns a component. This component is painted in the rectangle corresponding to the current table cell.

Then the renderer is called for the next cell, and the returned component (which has a different text and color, for example), is painted in the rectangle corresponding to the cell, etc.

Imagine that each time the renderer is called, a screenshot of the returned component is taken and pasted into the table cell.