Where the error is ?

[Buzdugan]

Hey !

I'm a fresh java programmer and doing some exercises from a book.
Got one that requires me to make a program that would read a number, and then give the coressponding value from Fibonacci's series (Without vectors/arrays), using the while function.

I've managed to get smt done, but the computer just waits for smt... I normaly would pursue the solution myself in order to learn smarter/better, but there is no error on compiling, or runtime.

A trained eye will spot the bug in a giff :

import java.io.*;

public class fibonacci {
	
	public static void main(String [] args){
		
		int fa = 1;
		int fb = 1;
		int fc = 0;
		int n = 0;
		
		BufferedReader tastatura = new BufferedReader(new InputStreamReader(System.in),1);
		String linie = "";
		
		try {
			
			System.out.println("Which Fibonnacci number shall it be?");
			linie = tastatura.readLine();
			n = Integer.valueOf(linie);
						
			int i=2;
			
			while (i <= n){
				
				fc = fa+fb;
				fb = fa;
				fa = fc;
			}
			System.out.println("the "n" number: " + n + "corresponds to: " + fc);
		}
		
		catch (IOException e)
		{
			System.out.println("error: " + e.toString());
		}	
	}
}

I know there is a smarter way to do this, but wanna try to get the juices out of my unevolved brain 1st.

The 'algorithm' was simple. Have 2 variables hold the initial values (global), outside the while loop, then just increment(change) each, based on the other's value(evolution).

Should work in theory....

I think it has something to do with using variables outside the loop, and writing values in variables outside the loop. I think it shouldn't be a problem (for me), but I'm sure that someone would give me a more than logical/reasonable explanation for not doing this.

[Fou-Lu]

PHP Code:

            while (i <= n){
                
                fc = fa+fb;
                fb = fa;
                fa = fc;
            } 


Neither i is incremented or n decremented. Because of this, the program infinitely loops since the condition is never fulfilled (eventually you'll run out of resources though and the program would crash ).

[renegadeandy]

Yep he is right - it will continue run those 3 lines forever.

Try adding :

i++;

to the bottom of your while loop!

[Buzdugan]

omg, I`m such a n00b. thanks guys !

I've even made it greater

fa=0;
fb=1;
fc=0;
			int i=1;
			
			while (i <= n){
				
				fc = fa+fb;
				fa = fb;
				fb = fc;
				i++;
			}