You need to check if there is an element x in treeset so that

-t <= x-nums[i] <= t. Also need to maintain the size k for treeset.

```
class Solution {
public boolean containsNearbyAlmostDuplicate(int[] nums, int k, int t) {
TreeSet<Long> ts = new TreeSet<>();
for (int i=0; i<nums.length; i++) {
// -t <= x-nums[i] <= t
if (ts.floor((long)nums[i]+(long)t) != null
&& ts.floor((long)nums[i]+(long)t) >= (long)nums[i]-(long)t) {
return true;
}
ts.add((long)nums[i]);
if (i >= k) {
ts.remove((long)nums[i-k]);
}
}
return false;
}
}
```