I can’t understand why I am getting this error despite `ceiling`

and `floor`

functions are present in the `TreeSet`

class. I get following error:

```
cannot find symbol: method ceiling(int)
```

Here is my Java code:

```
import java.util.Set;
import java.util.TreeSet;
public static boolean containsNearbyAlmostDuplicate(int[] nums, int k, int t) {
Set<Integer> set = new TreeSet<>();
for (int i = 0; i<nums.length; i++) {
Integer x = set.(nums[i]);
if(x!= null && x<= nums[i]+t)
return true;
Integer y = set.ceiling(nums[i]);
if(y!= null && nums[i]<= y+t)
return true;
set.add(nums[i]);
if(set.size()>k)
set.remove(nums[i-k]);
}
return false;
}
```