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