/**
* Creates two objects to improve performance of getValue(). The first object contains an array of
* values so that the getValue() function can return values based on an index, rather than using
* date calculations to extract the date from the Graphable. The second object contains a mapping
* which maps the current date to an offset in the newly created array.
*/
private void initialise() {
dateOffsets = new HashMap();
values = new ArrayList();
TradingDate endDate = (TradingDate) graphable.getEndX();
int offset = 0;
for (TradingDate date = (TradingDate) graphable.getStartX();
!date.after(endDate);
date = date.next(1)) {
values.add(graphable.getY(date));
dateOffsets.put(date, new Integer(offset++));
}
}
