14 First Position of Target

class Solution {
/**
 * @param nums: The integer array.
 * @param target: Target to find.
 * @return: The first position of target. Position starts from 0.
 */
public int binarySearch(int[] nums, int target) {
    //write your code here
    if (nums == null) return -1;
    int length = nums.length;
    if (length == 0) return -1;
    int start = 0;
    int end = length - 1;
    while (start + 1 < end) {
        int mid = start + (end - start) / 2;
        if (nums[mid] == target) end = mid;
        else if (nums[mid] < target) start = mid;
        else end = mid;
    }
    if (nums[start] == target) return start;
    else if (nums[end] == target) return end;
    else return -1;
}
}