Question

Fibonacci Sequence in JAVA

f(0) = 0, f(1) = 1, f(n) = f(n-1) + f(n-2)

Part of a code

public class FS { public static void main(String[] args){ IntSequence seq = new FibonacciSequence(); for(int i=0; i<20; i++) { if(seq.hasNext() == false) break; System.out.print(seq.next()+" "); } System.out.println(" "); } }

///Fill in the rest of the code!

Output

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181

You should define IntSequence as the interface.

You can't use for, while loop.

Thanks!!

Answer 1

IntSequence.java
------
public interface IntSequence
{
   public boolean hasNext();
   public int next();
}

FibonacciSequence.java
====

public class FibonacciSequence implements IntSequence {

   private int n;

   public int next(){
       int f = 0;
       int f1 = 0, f2 = 1;
       if(n == 0)
           f = 0;
       else if (n == 1)
           f = 1;
       else{
           for(int i = 2; i <= n; i++)
           {
               f = f1 + f2;
               f1 = f2;
               f2 = f;
           }
       }
       n++;
       return f;
   }
   @Override
   public boolean hasNext() {
       return true;
   }

}

FS.java
----
public class FS {
   public static void main(String[] args){
       IntSequence seq = new FibonacciSequence();
       for(int i=0; i<20; i++) {
           if(seq.hasNext() == false) break;
           System.out.print(seq.next()+" ");
       }
       System.out.println(" ");
   }
}

output
---
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181