Java 8 Lambda expressions for solving fibonacci (non recursive way)

Question

I am a beginner in using Lambda expression feature in Java 8. Lambda expressions are pretty well useful in solving programs like Prime number check, factorial etc.

H

Answer 1

The simplest solution is to use a stream of Pairs:

Stream.iterate(new long[] { 1, 1 }, p -> new long[] { p[1], p[0] + p[1] })
      .limit(92)
      .forEach(p -> System.out.println(p[0]));

Due to the lack of a standard pair type, it uses a two-element array. Further, I use .limit(92) as we can't evaluate more elements using long values. But it's easy to adapt to BigInteger:

Stream.iterate(new BigInteger[] { BigInteger.ONE, BigInteger.ONE },
               p -> new BigInteger[] { p[1], p[0].add(p[1]) })
      .forEach(p -> System.out.println(p[0]));

That'll run until you haven't enough memory to represent the next value.

By the way, to get the nth element from the stream:

Stream.iterate(new long[] { 1, 1 }, p -> new long[] { p[1], p[0] + p[1] })
      .limit(91)
      .skip(90)
      .findFirst()
      .get()[1];