Two Sum II - Input array is sorted

Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2.

Note:

Your returned answers (both index1 and index2) are not zero-based.
You may assume that each input would have exactly one solution and you may not use the same element twice.
Example:

Input: numbers = [2,7,11,15], target = 9
Output: [1,2]
Explanation: The sum of 2 and 7 is 9. Therefore index1 = 1, index2 = 2.

class Solution {
    public int[] twoSum(int[] numbers, int target) {
        if(numbers == null || numbers.length == 0){
            return null;
        }
        int left = 0;
        int right = numbers.length - 1;
        int[] res = new int[2];

        while(left < right){
            if(numbers[left] + numbers[right] == target){
                res[0] = left+1;
                res[1] = right+1;
                return res;
            }
            else if(numbers[left] + numbers[right] > target){
                right = right - 1;
            }
            else{
                left = left + 1;
            }
        }
        return res;
    }
}