// Fig. 23.24: FibonacciTask.java
// Task subclass for calculating Fibonacci numbers in the background
import javafx.concurrent.Task;

public class FibonacciTask extends Task<Long> {
   private final int n; // Fibonacci number to calculate

   // constructor
   public FibonacciTask(int n) {
      this.n = n;
   } 

   // long-running code to be run in a worker thread
   @Override
   protected Long call() {
      updateMessage("Calculating...");
      long result = fibonacci(n);
      updateMessage("Done calculating."); 
      return result;
   } 

   // recursive method fibonacci; calculates nth Fibonacci number
   public long fibonacci(long number) {
      if (number == 0 || number == 1) {
         return number;
      }
      else {
         return fibonacci(number - 1) + fibonacci(number - 2);
      }
   }
} 

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