An AggregateRenderer is used to render the TreeTable's aggregate rows. The aggregate renderer for a cell is taken with either specifying the row and column index for the cell, or the class of the cell's value:

public TableCellRenderer getAggregateCellRenderer(int row, int column);

public TableCellRenderer getDefaultAggregateRenderer(Class columnClass);

You can also set the based-on-class renderer with:

public void setDefaultAggregateRenderer(Class columnClass, TableCellRenderer renderer);

By default, TreeTable will install DefaultAggregateRenderer instances for all the basic classes (String, Object, Date, Boolean and Number).