What was the trigger for the calculation? How was it launched?

A trigger for calculation is usually an event or condition that initiates the execution of computations. In Java, this can be:

• A method call on an event (for example, a user action, data retrieval).
• A task scheduler (ScheduledExecutorService, Quartz) that starts the calculation on a schedule.
• An event from an external system or a message in a queue (for example, Kafka, JMS).

Example of scheduling a calculation using ScheduledExecutorService:

ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
scheduler.scheduleAtFixedRate(() -> {
    // calculation code
    System.out.println("Calculation is running");
}, 0, 1, TimeUnit.HOURS);

Thus, a trigger can be either an external event or an internal timer.