Search in Rotated array

Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). How do you find an element in the rotated array efficiently

 

public static int rotatedBinarySearch(int a[], int N, int key)
{
    int low =0;
    int high = N-1;
    
    while(low <= high)
    {
        int mid = (L+R)/2;
        
        if(a[mid] == key)
            return mid;
          
        //lower half is sorted 
        if(a[low] <= a[mid])
        {
            if(A[low]<= key && key < a[mid])
                high = mid -1;
            else
                low = mid +1;
        }     
        else   // upper half is sorted
        {
            if(a[mid] < key && key < a[high])
                low = mid + 1;
            else
                high = mid - 1;
        
        }       
    }
    
    return -1;
}