Fibonacci Series In Java With Recursion - Full Tutorial (FAST Algorithm)

Full tutorial for generating numbers in the Fibonacci sequence in Java, using Recursion!
The Fibonacci sequence (series) is often one of the first Java assignments teaching recursion for beginners.
The basic Fibonacci algorithm is very simple, but works extremely slowly. This improves on that Fibonacci algorithm and generates Fibonacci numbers FAST.
We'll walk through the entire Fibonacci series algorithm step by step, and walk through coding the entire thing in Java.
Learn a great Java Fibonacci sequence program by watching the whole algorithm being described and coded.
Learn or improve your Java by watching it being coded live!
Hi, I'm John! I'm a Lead Java Software Engineer and I've been in the programming industry for more than a decade. I love sharing what I've learned over the years in a way that's understandable for all levels of Java learners.
Let me know what else you'd like to see!
Links to any stuff in this description are affiliate links, so if you buy a product through those links I may earn a small commission.
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[@Sami67995]

Everyone can be a java programmer but to be a java teacher It takes a lot of effort Thank you John

[@Avarn388]

You’ve earned my sub. I’ve been working out a similar problem with Python so your refresher was really helpful. I will definitely utilize this for my assignment.

[@Guide4Ever]

This was one of the best and well delivered tutorials! Kudos to you!

[@MTB_Bay_Area]

Clear, and to the point like all your videos. Thank you for helping.

[@faganyusifli9039]

The best explanation of Fibonacci with recursion so far!

[@belkhirisub9115]

Honestly, I was struggling to understand Fibonacci in high school, but now I understand everything well I wish you were my programming teacher

[@jonsantos6056]

Very useful for learning recursion especially if dealing with slow speed computations. *Tip: Primitives can never be assigned 'null', instead, they will default to 0.*

[@JimFikes]

Thanks, John. Your explanations are always so helpful.

[@cstrovn]

Thank you for this beautiful tutorial. I'd never programmed in Java till this week when I decided to make a personal project entirely in it. It was painful but I made it through. This tutorial definitely helped a lot.

[@asankasiriwardena3383]

a fairly easy implementation without recursion, int n = 10; int[] arr = new int[n]; arr[1] = 1; for (int i = 2; i < n; i++) { arr[i] = arr[i - 1] + arr [i -2]; } System.out.println(Arrays.toString(arr));

[@farkhodkuchkarov5238]

Thank you so much for such an effective tutorial dude! I love it!

[@pradeepyadav2562]

clear , consice and crisp

[@robertb5357]

Great and easy explanations of many java topics. Keep up the good work

[@dondigidon1633]

John, thank you! You do great content! 👍👍👍👍👍

[@evanderoos9547]

Thanks bro, you have no idea how much this helped

[@brandonsullivan4866]

Amazing video sir! Thank you for the knowledge.

[@iamabhik]

Has to be the simplest and best ways to explain concepts...kudos

[@svalyavasvalyava9867]

Thanks a lot for all the effort!!!

[@u2bMusicBeauty]

What an amazing video, I am getting more and more interested in Java! +100👍

[@totem3700]

I always wanted to learn about recursion and I like the fibonacci sequence. This video was really helpfull

[@DavidOliveira-tm9bj]

John, you're a legend!

[@moaly4738]

Very interesting and well explained as Always

[@front-endfatih4030]

My favorite one yet

[@lucasteixeira1631]

awesome video! very detailed and full of useful info

[@BoMpOwMsp]

So helpful, thanks!!

[@arsalali7836]

Great work man !

[@gongdian123]

The amazing code, i never seen it, high effectiveness

[@Gandobilis]

Awesome tutorial!

[@tusharnagare6409]

I just love you videos very smart explanation to all the concept. Keep up the good work :)

[@enriquecabral-mixco1337]

Great video!

[@fremontlowe1]

Thanks for this tutorial. I found it to be extremely helpful. I even changed the cache variable to BigInt to increase the size of fibonacci numbers returned. I no longer saw negative numbers; and still executed in sub seconds.

[@2k7Bertram]

Bro I wish you were my Java prof back in college. Excellent!

[@mouhebmanai]

Thank you for giving all of these informations all for free

[@mdstrapa]

your content is amazing!

[@evanserickson]

Love the video! Let's see some full stack tutorials for back end. Like spring and credit card processing

[@emerson3070]

Thanks John!!

[@surendharv795]

Thank you john !

[@Mildimage]

Very cool and amazing content man!

[@PortgueseProBF3]

Whoa this is amazing, didnt even think of that

[@mariamaamir1116]

Thank you so much this truly helped me!!!!!!!

[@lumilo7]

GRacias pelaooo! ♥

[@fathimasyed4232]

Good tutorial. Thank you.

[@titasroy2923]

Love you sir ! Take my good wishes

[@MrDarshD]

Well explained and coded! Loved the way you described small details like why we do n-1 and n+1!! Also appreciate the bonus at the end with all numbers printed. Thank you so much John!

[@sianke1991]

Very Helpful.

[@jackofnotrades15]

Man...This guy... Is just ossum...

[@kishordige9721]

Thank you very much. Explained Simply.

[@CodingWithJohn]

Thanks! Glad it helped

[@user-po9tk8mi4t]

Good explanation

[@dsar8727]

Hey John, love the Epi SG. And Rush are amazing.

[@m.shahrim1933]

Well explained

[@javidaghayarli8252]

Thank you

[@shwetayadav4244]

Amazin explanation

[@mihirgore4074]

You rock dude !

[@mist3rshey2nil]

well done!

[@pranjalnama2420]

thank you

[@DK-fn6xr]

This is how I learned about stack overflow error.

[@yourcasualdeveloper]

Great video

[@nibbler7]

Man your videos are a lifesaver! Could you do a video on lambdas? It would be very appreciated!

[@marathistates]

Thanks jon Bhai i am from India🇮🇳 😍

[@jesusayala1342]

Thank you very much for all the effort dear John!!! I like all your content, it helps us to learn a lot!! please don't stop teaching us =) I was thinking of simplifying a bit the code you teach us in your video, but I'd like your opinion: private static long fibonacci(int n){ if (n

[@KaisarAnvar]

I love the fact that you don’t use auto-prediction while you’re typing. I want to disable mine too but don’t know how. I use IntelliJ and VSCode.

[@vpenywise]

Brutal... It all seems so easy, so logical, so natural... But then you try to code it yourself and... woof! :D

[@alexandercvetkov4269]

Repetition is the mother of all knowledge. :D The fundament is easy and natural, to be able to apply the fundament - it takes practice. And practice is the child of repetition. I was like that with two-dimensional arrays - the two indexes confused me to a level beyond 14 year old girl, watching a chick-flick. Now i do them fine. :D I guess a guy must be more stubborn than the actual thing he wants to learn.

[@immythic8351]

Sir, you're massive!! I'm still trying to understand a part of the video but it's brilliant! I thought about using a hash map but I think it would be pretty similar to using an array, right?

[@zeuss_2122]

Thanks for the video. I really learn alot from your videos. I can see how to reverse a binary tree please. 🙏🙏 Thanks in advance

[@navjotsingh2457]

Ty

[@bennyibmnkonga1122]

very cool! the cache help to reduce the complexity of the fibo algorithme to O(n) instead of O(n^2) i found it very amazing and i like, thank you JOHN!

[@raz0229]

or store the values of n in an array upto 100 or something and just return them so you always get O(1) to impress your teacher. LOL

[@AlexandruTimus]

You can get O(1) by doing the calculation in a mathematical way. You you search on internet there are some formulas that can calculate the Nth number in just one line of matemathic operations.

[@theALFEST]

Iterative algorithm is much faster and doesn't need cache

[@bolbans]

@@theALFEST would you mind sharing?

[@theALFEST]

@@bolbans for (int i = 3; i

[@haltsmaul.]

To calculate all Fibonacci's up to n, you could have used the cache array instead of using a for loop to calculate each n.

[@tubememax]

We could also use a hash map to store results over more than one calculation.

[@07Flash11MRC]

Great video. Can you do Bernoulli Numbers next, please?

[@ahmedbishree9429]

Thanks, John you are amazing, I want to ask you, instead of using a normal array or hash map is there any library for the cache in java?

[@mrchr0no]

Awesome

[@danielmdubois]

Nice video. I understand why you skipped over it, since the focus was on teaching recursion, but I think it would be worth taking a moment at the point when you introduce a for loop to mention that you could have avoided all the recursion entirely with an interative solution. (At least you're saving the memoization from call to call!)

[@FredrickIrubor]

Using a for loop and array worked just fine with fast speed public class FibonnaciLoop { private static long[] fibArr; public static void main(String[] args) { int n=50; fibArr = new long[n+1]; fibArr[0]=0; fibArr[1]=1; for (int i=2; i

[@danielmdubois]

@@FredrickIrubor You don't need to allocate an array; you can get by with updating and storing nMinus1 and nMinus2 each iteration.

[@brightmatter]

interesting, I made one of these with an iterative approach to add up a particular diagonal in pascal's triangle. I think i hit a wall sooner than n=92 though. i'll have to go back and see why that was.

[@uncopino]

i was playing around with recursion yesterday and i made a fibonacci recursive algorithm as fast as yours but using no static variables. i just made the method return an array of 2 longs (the last two values) in order to avoid the double recursive call. i can post the code if anyone’s interested

[@CodingWithJohn]

Go for it!

[@uncopino]

@@CodingWithJohn it should throw an IllegalArgumentException when given n < 2, i know. anyway, here it is: public static long[] last2fibonacciValues(long n) { long[] last2values = {0, 1}; if(n

[@krishnanath08]

I'm feeling energized now. Practicing java again after 9years. I do not remember anything at all taking it slow n steady and watching your videos to clear my doubts

[@phekev]

Great and simple explanation. Can I give a +1 to the generics suggestion a d suggest a video about ternary operators

[@FloStudios]

Interesting facet about this caching method...you don't even need to write a loop and run fibonacci() n-times. Just run it once and the cache should have the whole sequence! Print the array space delimited.

[@myguy2656]

Can Someone explain how he gets f(6) = f(6-1) + f(6-2) =8? Because when i add it up i get 5+4=9…

[@urosjovanovic1864]

I have viewed many coding videos but I must say never have I ever found that somebody explains it so good. Just keep making videos, it suits you so much. Regards from Serbia :D

[@emekaukwuoma3359]

Nice video John. Out of curiosity, is it possible to have the cache within the method?

[@ravitrivedi9588]

Thank you so much for the simple explanation john!!!!!!!!, I just have a tiny question to ask , Why are you creating a Cache in main method can't we directly create it inside the fibonacci function itself ? As its using mainly over there

[@vitcermak7737]

As a junior software engineer (Java dev) I gotta ask you - where have you been 2 years ago when I was sweating bullets on programming exercises like this?! :D

[@giftbanda9795]

public static void main(String[] args) { Map memo = new HashMap(); int result = fibonacci(5, memo); System.out.println(result); } /** * Calculates the nth Fibonacci number using memoization. * Time Complexity: O(n) where n is the value of the input number. * Space Complexity: O(n) for storing the memoization map and the recursive call stack. */ public static int fibonacci(int num, Map memo) { if (num

[@nate6199]

Do you think you could explain reading and writing input from a file? Love your videos.

[@dilln2158]

He already did

[@diyaa_hudaib5263]

U are great maaaannn can u explain how can i put every element in GUI separated on lines and put thim exactly on the spot that i think?

[@elmehditalbi8972]

Hello John, I'm asking once again if generics can be done in a video explained by you. Please I'm having trouble with the content, and your explanation is magnificent !

[@CodingWithJohn]

I do plan to have a generics video sometime, it just depends on if I have enough time during any given week to make the video on that particular topic. Some take quite a bit long to put together than others!

[@elmehditalbi8972]

@@CodingWithJohn thank you so much

[@joshlicew6691]

Bro generics are so easy. Lets say for example you have a ArrayList, I cant pass a string, or a double, or any other type other than a Integer. NOW with a generics class you replace where you would put the type to a letter, it can be any letter, but usually E. So now im going to say ArrayList. Now the type is a generics type which means i can now say ArrayList, or Arraylist, its just like think of it as a variable. It chances based on the use

[@timothymattnew]

@@CodingWithJohn yep, the video is very needed)

[@lucasteixeira1631]

he made it! Generics In Java - Full Simple Tutorial kzbin.info/www/bejne/gWLMpmShjdCJpaM

[@emerson3070]

6:12 You remind me of the Dean from 'Community' the show lol :)

[@timm1328]

let phi = (1+sqrt(5))/2 then fib(n)= (phi^n - (1-phi)^n)/sqrt(5). no recursion and returns values as large as a double can hold and accepts any positive double as input not just integers

[@tvclipsgames1338]

that is why long value is very very long 👍👍

[@LaszloHadadi]

Hello John, First of all the content is great! I think your reasoning why you need to size the cache to be n +1 is not 100% correct: Basically you never used the cache[0] as when f0 caculated you return with 0 in line 19. Also I would arguing with the condition in line 18 because for fibonacci(-2) it would return with -2 which is technically invalid and I rather would throw an exception when So my method would look like this (of course let's not talk about conccurency issues during the cache population): private static long fibonacci(int n) { if (n

[@CodingWithJohn]

Yes, you can keep your cache size "n" but then you have to offset the index by 1 when storing/looking up values, which I think just leads to more confusion. But if you really want to you can make it "n" instead and do that, you can do it. And I agree that for a super robust method, it should throw exceptions when negative values are entered. I haven't tried running your code myself, but I think it needs to account for the condition where n = 1 also. If it isn't coded explicitly to return 1, I think it will try calling fibonacci(n - 2), which would be fibonacci(-1) and throw an exception. Thanks for watching, and for the great comment!

[@fesd2010]

you can use BigInteger to get higher numbers

[@shyamsoni5389]

WOW!

[@omaribrahimmemories]

how does the code store? isn't when the project is off the still will return to null so if it have been to calculate again it will take same time, i didn't understand this thing

[@dianamirlanbekova5894]

Hi John, why 0 is not being counted as 1st number in fibonacci sequence? If I type 3, it results 0 1 1 2. It should've print out 0 1 2

[@Mu7ammad]

is there a way to solve the problem of limitation like what if I use wrapped numbers?

[@sysybaba420]

Well explained and coded!!! Can we use Integer[] instead to avoid negative values?

[@Jancirubi]

We can use BigInteger instead to avoid negative values. This will cover wide range of values.

[@vladislavstashek2063]

The way you explain is mesmerising! But I have a question, how can we find the 100th Fibonacci number ?

[@YeniCorrea]

I would dare to say, using BigDecimal instead of long because that datatype can store bigger numbers.

[@djwebm6653]

Nice video, but im debating with myself if the cache was really needed aswell. Wouldnt it be possible to pass trough the destination n, the current n previous number and this number recursivly? I might be in the wrong here tho but Something like this: fibbonachi(int destN, int currentN, int previous, int number) The method would just add the numbers and send through the new number and the number variable. And then whenever the destN is equal to the currentN it would stop recurring

[@kunalkheeva]

Could you please start solving leetcode problems as well?

[@Nbak-cw7jx]

Hello thank you for this tutorial, but what if the user will be the ones to choose the start and end point of the Fibonacci like the user chooses 55 as the starting point and 987 as the end, and it must dispay 55 to 987 without displaying the series before 55

[@JesseLinseman]

Simply change the bounds of the for loop he showed in the video to include this user entry. e.g. if user entered start = 55, end = 987, the loop would be changed to the following: for(int i = start; i