this got me confused on why it needs and when I did it right it says it wouldn't work because java

Modify the existing ArrayLists's contents, by erasing the second element, then inserting 100 and 102 in the shown locations. Use ArrayList's remove() and add () only. Sample ArrayList content of below program: 100101102103 \begin{tabular}{r|r} 1 & import java.util. ArrayList; \\ 2 & \\ 3 & public class ArraylistADT \{ \\ 4 & \\ 5 & public static void main (String [] args) \{ \\ 6 & Arraylist numsList = new Arraylist O); \\ 7 & int num0fElem =4; \\ 8 & \\ 9 & numsList.add(101); \\ 10 & numsList.add(200); \\ 11 & numsList.add(103); \\ 12 & \\ 13 & K Your solution goes here / \\ 14 & \end{tabular}