Aggregators calculate and return values for the aggregate rows of a TreeTable component. The value for the cell of an aggregate row is calculated with:

public Object getAggregateValue(AggregateRow node, int columnIndex);

Then, the value is assigned on the row with:

public Object prepare(AggregateRow row, int columnIndex);

, which ensures that aggregate values are not calculated repeatedly.

DynamicTreeTableModel defines methods for creating, assigning and retrieving the aggregators:

protected Aggregator createDefaultAggregator();

public void setDefaultAggregator(Aggregator aggregator);

public Aggregator getAggregator(int columnIndex);

public Aggregator getDefaultAggregator();

By default, a DefaultCellAggregator is created which uses the installed TreeTableComparators to calculate the aggregate cell values.