Write a program using LinkedList class and ListIterator interface to demonstrate the following activities:

1. Create a singly linked list named "Alphabets" with four elements: "P", "Q", "R", and "T" in the same sequence. Create an iterator named "iter1" and attach it to the linked list.

2. Add a new element "O" at the beginning of the linked list.

3. Add a new element "U" at the end of the linked list.

4. Add a new element "S" after the element "R".

5. Remove the element "O" and "Q".

6. Display the linked list after performing each activity 1 to 5.

Sample output:

[P, Q, R, T]

[O, P, Q, R, T]

[O, P, Q, R, T, U]

[O, P, Q, R, S, T, U]

[P, R, S, T, U]