LeetCode-Range Sum Query- Immutable

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.

Example:

Given nums = [-2, 0, 3, -5, 2, -1]

sumRange(0, 2) -> 1
sumRange(2, 5) -> -1
sumRange(0, 5) -> -3

Note:

1. You may assume that the array does not change.
2. There are many calls to sumRange function.

Solution:

public class NumArray {
    int[] sums;
    public NumArray(int[] nums) {
        sums = new int[nums.length];
        int sum = 0;
        for (int i=0;i<nums.length;i++){
            sum += nums[i];
            sums[i] = sum;
        }
    }

    public int sumRange(int i, int j) {
        int sum1 = (i==0) ? 0 : sums[i-1];
        int sum2 = sums[j];
        return sum2 - sum1;
    }
}


// Your NumArray object will be instantiated and called as such:
// NumArray numArray = new NumArray(nums);
// numArray.sumRange(0, 1);
// numArray.sumRange(1, 2);