public class MyClass {
    public static void main(String args[]) {
        int[] arr = {1, 3, 5, 7, 8};

        int idx = findLocalPeak(arr, 0, arr.length - 1);
        System.out.println(String.format("Result: index = %d, value = %d", idx, arr[idx]));
    }

    public static int findLocalPeak(int[] arr, int left, int right) {
        int n = right - left + 1;
        if (n==1) { return left; }
        if (n == 2) {
            if (arr[left]>=arr[right]) {
                return left;
            } else {
                return right;
            }
        }

        int mid = (int)Math.floor(n/2) + left;
        if (arr[mid-1]<=arr[mid]&&arr[mid+1]<=arr[mid]) {
            return mid;
        } else {
            if (arr[mid-1]>arr[mid]) {
                return findLocalPeak(arr, left, mid-1);
            } else {
                return findLocalPeak(arr, mid + 1, right);
            }
        }
    }
}