Total Occurrence of Target

public class Solution {
    /**
     * @param A an integer array sorted in ascending order
     * @param target an integer
     * @return an integer
     */
    public int totalOccurrence(int[] A, int target) {
        // Write your code here
        if (A == null || A.length == 0) {
            return 0;
        }
        int first = findFirstIndex(A, target);
        if (first == -1) {
            return 0;
        } 
        int last = findLastIndex(A, target);    
        if (first == -1) {
            return 0;
        }
        return last - first + 1;
    }
    
    private int findFirstIndex(int[] A, int target) {
        int start = 0;
        int end = A.length - 1;
        
        while (start + 1 < end) {
            int mid = start + (end - start) / 2;
            if (A[mid] == target) {
                end = mid;
            } else if (A[mid] < target) {
                start = mid;
            } else {
                end = mid;
            }
        }
        
        if (A[start] == target) {
            return start;
        } 
        if (A[end] == target) {
             return end;
        }
        return -1;
    }
    
    private int findLastIndex(int[] A, int target) {
        int start = 0;
        int end = A.length - 1;
        
        while (start + 1 < end) {
            int mid = start + (end - start) / 2;
            if (A[mid] == target) {
                start = mid;
            } else if (A[mid] < target) {
                start = mid;
            } else {
                end = mid;
            }
        }
        
        if (A[end] == target) {
             return end;
        }
        if (A[start] == target) {
            return start;
        } 
        
        return -1;
    }
}