Skip to content

Fibonacci Streaming in Java

The challenge

You’re going to provide a needy programmer a utility method that generates an infinite sized, sequential IntStream which contains all the numbers in a fibonacci sequence.

A fibonacci sequence starts with two 1s. Every element afterwards is the sum of the two previous elements. See:

1, 1, 2, 3, 5, 8, 13, ..., 89, 144, 233, 377, ...

The solution in Java code

Option 1:

import java.util.function.IntSupplier; import java.util.stream.IntStream; public class Utility { public static IntStream generateFibonacciSequence() { return IntStream.generate(new IntSupplier() { int a = ; int b = 1; @Override public int getAsInt() { int x = a + b; a = b; b = x; return a; } }); } }
Code language: Java (java)

Option 2:

import java.util.stream.Stream; import java.util.ArrayList; import java.util.List; import java.util.stream.IntStream; public class Utility { public static IntStream generateFibonacciSequence() { return Stream.iterate(new Integer[]{1, 1}, p -> new Integer[]{p[1], p[] + p[1]}) .mapToInt(integers -> integers[]); } }
Code language: Java (java)

Option 3:

import java.util.stream.IntStream; import java.util.stream.Stream; import java.util.concurrent.atomic.AtomicInteger; public class Utility { public static IntStream generateFibonacciSequence() { AtomicInteger fibonacci = new AtomicInteger(1); return IntStream.iterate(1, x -> fibonacci.getAndAdd(x)); } }
Code language: Java (java)

Test cases to validate our solution

import org.junit.Test; import java.util.PrimitiveIterator; import static org.junit.Assert.assertArrayEquals; import static org.junit.Assert.fail; public class TestSuite { @Test public void testThatTheFirstTwentyElementsAreCorrect() { assertArrayEquals("The first twenty elements are incorrect!", new int[] {1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765}, Utility.generateFibonacciSequence().limit(20).toArray()); } @Test(timeout = 30) public void testRecursivePropertyInStreamByRandomLeaps() { for (int i = ; i < 3; i++) { // Repeat three times final PrimitiveIterator.OfInt iterator = Utility.generateFibonacciSequence() .skip((int) (Math.random() * 900)) // Begin leap .limit(20) // End leap .iterator(); int previous = iterator.nextInt(), current = iterator.nextInt(); while (iterator.hasNext()) { final int next = iterator.next(); if (next != previous + current) fail(String.format("Elements %s, %s are followed by %s!", previous, current, next)); previous = current; current = next; } } } }
Code language: Java (java)

See also  How to Resolve Scaling Squared Strings in Java
Tags:
Subscribe
Notify of
guest
0 Comments
Inline Feedbacks
View all comments
0
Would love your thoughts, please comment.x
()
x