FastFibonacci.java

package nl.hva.dmci.ict.se.datastructures.fibonacci;

import java.math.BigInteger;
import java.util.function.Consumer;

import edu.princeton.cs.algs4.Stopwatch;

public class FastFibonacci {
    
    static double timeStart;
    static int fiboNumber = 0;

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        final int SIZE;

        if (args.length == 0) {
            SIZE = 100;
        } else {
            SIZE = Integer.parseInt(args[0]);
        }

        Stopwatch stopwatch = new Stopwatch();
        FibjesMachine fibonator = new FibjesMachine(SIZE);

        System.out.printf(" n %15s  (  lap \t total)\n", "fib(n)");
        timeStart = stopwatch.elapsedTime();
        fibonator.iterate((BigInteger fibje) -> {
            double timeEnd = stopwatch.elapsedTime();
            double lapTime = timeEnd - timeStart;
            fiboNumber++;
            System.out.printf("%2d %15d  (%.3f \t %.3f)\n", fibje, fiboNumber, lapTime, timeEnd);
            timeStart = stopwatch.elapsedTime();
        });

    }

    private static class FibjesMachine {
        BigInteger[] fibjes;
        int nextFibjeIdx;

        public FibjesMachine(int fibjesAmount){
            fibjes = new BigInteger[fibjesAmount];
            nextFibjeIdx = -1;
        }

        public void iterate(Consumer<BigInteger> con){
            for(int i=0; i < fibjes.length; i++){
                con.accept(nextFibje());
            }
        }

        public BigInteger nextFibje(){
            nextFibjeIdx++;
            if(nextFibjeIdx < 2 ){
                fibjes[nextFibjeIdx] = BigInteger.valueOf(1);
                return BigInteger.valueOf(1);
            }
            else {
                fibjes[nextFibjeIdx] = fibjes[nextFibjeIdx - 2].add(fibjes[nextFibjeIdx -1]);
                return fibjes[nextFibjeIdx];
            }
        }

    }
}

Fibonacci.java

package nl.hva.dmci.ict.se.datastructures.fibonacci;

import edu.princeton.cs.algs4.Stopwatch;

/**
 * A small program that calculates Fibonacci numbers.
 * This program is used by students to investigate the Fibonacci algorithm.
 * 
 * @author Huub van Thienen
 * @author Nico Tromp
 */
public class Fibonacci {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        final int SIZE;

        if (args.length == 0) {
            SIZE = 100;
        } else {
            SIZE = Integer.parseInt(args[0]);
        }

        Stopwatch stopwatch = new Stopwatch();

        System.out.printf(" n %15s  (  lap \t total)\n", "fib(n)");
        for (int n = 1; n <= SIZE; n++) {
            double timeStart = stopwatch.elapsedTime();
            long fiboNumber = fib(n);
            double timeEnd = stopwatch.elapsedTime();
            double lapTime = timeEnd - timeStart;
            System.out.printf("%2d %15d  (%.3f \t %.3f)\n", n, fiboNumber, lapTime, timeEnd);
        }
    }

    /**
     * Berekent het n-de Fibonacci-getal.
     * 
     * @param n Het hoeveelste Fibonacci-getal
     * @return De waarde van het Fibonacco-getal
     */
    public static long fib(int n) {
        if (n < 2) {
            return n;
        } else {
            return fib(n - 1) + fib(n - 2);
        }
    }
}

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