For loop inside a while loop, what order is that in big o??

Question

If say I have a for loop inside a while loop, then is that suppose to be in the order of O(n^2) right?? Is there any possibilities to change this into the order of O(n)??

Answer 1

the other size and the temp size is abstact, which can be defined. This is actually for my union method, my teacher asks me to write this method using the order of O(n) which I think it is not possible. What do you guys think??
Below is the code I have made:
public Set<E> union(Set<E> other) {
          int count = 0;
          Iterator<E> iterator1 = other.iterator();
          while (iterator1.hasNext())
               count++;
          Object[] temp = new Object [data.length+count];
          n = data.length+count;
          for (int i = 0; i<count; i++)
               temp[i] = data;
          for (int j = count; j<temp.length; j++)
               temp[j] = iterator1.next();
          data = temp;
          return null;
but it still has same elements on it and I am thinking of a way on how to remove those same elements