Could be done in more optimised way by storing total sum and calculating rsum & lsum at runtime using total sum. 

    public int[] findDifferenceArray(int[] nums) {
        int n = nums.length;
        int[] differenceArray = new int[n];
        // TODO: Write your code here
        int sum=0,lsum=0;
        for (int i : nums){
          sum+=i;
        }

        for(int i=0;i<nums.length;i++){
          int rsum = sum-nums[i]-lsum;
          differenceArray[i]=Math.abs(rsum-lsum);
          lsum+=nums[i];
        }
        return differenceArray;
    }