Sliding window Algo-> Maximum sum of subarray

class Main {
    
    public static int maxSubArray(int[] nums, int k){
        int currentSum = 0;
        
        //Find sum of first window
        for(int i=0; i<k; i++){
            currentSum= currentSum + nums[i];
        }
         int maxSum= currentSum;

        //slide window
        for(int j=k;j<nums.length;j++){
            currentSum= currentSum + nums[j] - nums[j-k];
            maxSum= Math.max(currentSum, maxSum);
        }
        return maxSum;
    }
    
    public static void main(String[] args) {
        int nums[] = {1,5,4,2,9,9,9};
        int k = 3;
        System.out.println(maxSubArray(nums, k));
    }
}