Thread: Fibonacci Series

For an assignment I'm trying to create a dynamic array (I'm not allowed to use an array list) that has an equation write the Fibonacci series to the array and then print that array. The only problem is that it tends to write only numbers (completely unrelated to fibonacci) or a bunch of zeros then a 35 at the end. I'm just beginning in java and I could use some help correcting the code.

 
import java.util.Scanner;
 
	public class Fibonacci {
 
 
 
	public static void main(String[] args) {
 
		int[] numbers;
		Scanner scan = new Scanner(System.in);
		System.out.println("How many numbers would you like to solve to in the Fibonacci series?");
 
 
		int num;
 
 
 
		num = scan.nextInt();
 
		numbers = new int[2];
 
 
		numbers[0]=0;
		numbers[1]=1;
			for(int x =2; x<num; x++){
				numbers = new int[x+1]; //Increases array size
				numbers[x]=((x-2)+(x-1)); //places Fibonacci value in index
		}
 
		for(int i = 0; i < numbers.length; i++){
			System.out.println(numbers[i]);
		}
 
 
	}
 
}

It increases the size of the array, but as it doesn't copy the contents that's why they are all zeros. Yet that doesn't explain why the last number is 35 when it shld b in the thousands.

Would you be able to explain?

--- Update ---

Originally Posted by helloworld922

numbers[x]=((x-2)+(x-1));

Take a careful look at this line and you may find your second problem.

That is the equation for the Fibonacci series unless I'm mistaken. And since the equations are both in parentheses it shouldn't matter.

I recommend you to use java.utils.Arrays.copyOf(originalArray, newLength). This will return you a copy of this array, but with newLength size.
The line

numbers = new int[x + 1];

is equivalent to

numbers = null;
numbers = new int[x + 1];

that is, number starts to point to a completely new array, created by new int[x + 1]. All new integer arrays automatically initialize all their elements to 0.

Also,

numbers[x]=((x-2)+(x-1));

Is incorrect. x is an index of an element in an array. Hence, (x - 1), for example, is NOT a previous number, but it's index. Use numbers[i] to access a number at the index i.

P.S.: Increasing dynamic array by 1 element at a time is pretty inefficient, because every appending to an array requires duplicating of this array. Instead, I suggest you to double the array when you need extra space.