```
private int[] nums;
public NumArray(int[] nums) {
this.nums = nums;
int length = this.nums.length;
for (int i = 1; i < length; i++) {
nums[i] += nums[i - 1];
}
}
public int sumRange(int i, int j) {
if (i == 0) return nums[j];
return nums[j] - nums[i - 1];
}
}
// Your NumArray object will be instantiated and called as such:
// NumArray numArray = new NumArray(nums);
// numArray.sumRange(0, 1);
// numArray.sumRange(1, 2);```
```