Download jFin and install the distribution.
Then take a look at the examples and their source:
Follow the instructions in the installation directory for the WAR file. The home page for the jfin web application has links to the three example web services and the AJAX enabled plain swap application:

From your shell type (without any parameters):
cd examples
./SwapScheduleGenerator.sh
This will generate a schedule for an imaginary 1M EUR 10 Year interest rate swap, with quarterly fixed and floating periods adjusted following. The output includes the offset fixing date, and the payment amounts calculated using Actual/Actual:

The day count fraction calculator is used:
DaycountFractionCalculator.sh startDate(YYYY/MM/DD) endDate(YYYY/MM/DD) holidayCalendar daycountBasis