Solution.java

class NumArray {

    private int[] sums;

    public NumArray(int[] nums) {
        int n = nums.length;
        sums = new int[n + 1];
        for (int i = 0; i < n; ++i) {
            sums[i + 1] = nums[i] + sums[i];
        }
    }
    
    public int sumRange(int i, int j) {
        return sums[j + 1] - sums[i];
    }
}

/**
 * Your NumArray object will be instantiated and called as such:
 * NumArray obj = new NumArray(nums);
 * int param_1 = obj.sumRange(i,j);
 */