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Java Newbie "Fibonacci Sequence"  RSS feed

 
Jb Anderson
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Hello Again. To reiterate, I am a newbie attempting to learn Java through iTunes Stanford CS106a and Eric Roberts' "Art and Science of Java." I am not a student nor am I enrolled in any class. I am attempting a programming exercise (chp. 4, ex. 9) to display the values in the Fibonacci sequence from F0 to F15. I understand the concept, but, for some reason my equation is simply creating a resulting string of numbers that simply increase by 2's. Very frustrating. As, I know it is supposed to be the sum of the previous F and the F that precedes that one to total the new F number. It seems so simple yet I seem to be far off. As usual, I have worked my code for your review. Any and all help is always greatly appreciated!

 
Winston Gutkowski
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Jb Anderson wrote:I understand the concept, but, for some reason my equation is simply creating a resulting string of numbers that simply increase by 2's.

Those two statements sound contradictory.

As, I know it is supposed to be the sum of the previous F and the F that precedes that one to total the new F number.

Yes, but what is F? It definitely isn't the current index, which is all your program is working with.

My suggestion: StopCoding (←click), and have another look at the formula. If you're still having problems, come back and we can help you further.

Tip: You might want to think about using an array (or a List) to keep previous values of 'F', but it's not strictly necessary.

Winston
 
Douglas Knapp
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JB, I'm not able to find that course in iTunes. Is there a link?
 
Tim Cooke
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Winston is right. From looking at your code I think you have misunderstood how the Fibonacci Sequence is derived.

The formula is Fn = Fn-1 + Fn-2. With seed values F0=0, F1=1.

Start small. Get your code working for small values of n.
Start at n=0. What is the expected outcome? What about where n=1?
n=0. Sequence [0]
n=1. Sequence [0,1]
n=2. Sequence [0,1,1]
n=3. Sequence [0,1,1,2]

Take a look at how you are calculating the value of Fn. Are you calculating Fn = Fn-1 + Fn-2? Or are you calculating Fn = (n-1) + (n-2)?

I would also recommend that you base your if conditions on the current value of f rather than total, it's not clear what the significance of it being less than 0 and whether it's -3 or not is. Given that the value of total, which should be the current Fib sequence value, is not right then when you fix that then your if condition will fall apart causing you more confusion.
 
Mangal Pandey
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Your variable SENTINEL will print up-to F16 though you need F15, make it 15.
 
Jb Anderson
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Tim,

Thank you very much for your reply. I was hoping for someone to evaluate my code and then nudge me so I could see what I was actually doing and how it differed from what I needed to do. Your response has greatly helped me re-focus my approach. Not being a "math-person" I was getting a bit flummoxed with the actual Fibonacci equation which then resulted in a flawed translation to Java coding.

Thank you, Tim, for taking the time to examine my code and realize what I needed to be told so I could refine things on my own.

I will go back to the woodshed and re-post with (hopefully) a successful program.

-JB
 
Jb Anderson
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Mr. Pandey,

Thanks for pointing out that mistake. It was an oversight on my part. I appreciate your input.

-JB
 
Jb Anderson
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Douglas,

The course can be found on iTunes U. It won't be listed in the "normal" iTunes storefront. Download the iTunesU app to access the available courses.

-JB
 
Douglas Knapp
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Thanks, JB. I haven't yet wrapped my head around iTunes U.
 
Tim Cooke
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Jb, How are you getting on?
 
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