Thread: Index -1 out of bounds

Can someone explain that error? I do not get what they mean by saying "Index -1", I don't have such an index in my code ??

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 17
        at LengthSequence.main(LengthSequence.java:16)

from this code

 int[] numbers = { 1, 1, 2, 3, 3, 4, 5, 2, 4, 5, 6, 7, 8, 9, 6, -1, -2 };
        System.out.println("Original array: " + Arrays.toString(numbers));
 
        int count = 0;
        ArrayList<Integer> consLength = new ArrayList<Integer>();
        for (int i = 0; i < numbers.length; i++) {
            System.out.println("Index i : " + i);
            if (numbers[i - 1] <= numbers[i]) {
                count++;
            } else {
                consLength.add(count);
                count = 0;
            }
        }
        System.out.println(Collections.max(consLength) + 1);

--- Update ---

I got it. Since we compare i-1 and 1. That's why.