You can't use remove on the list while using the "for each" loop. Instead, you can use this to call remove on the iterator:
Iterator<Integer> iterator = list.iterator();
while(iterator.hasNext()) {
Integer integer = iterator.next();
// ...check if you want to remove this one...
iterator.remove();
}
If you actually want to replace every value with "200", or replace with some other value, it might make more sense to build up a new list:
List<Integer> newList = new ArrayList<Integer>();
Iterator<Integer> iterator = list.iterator();
while(iterator.hasNext()) {
Integer integer = iterator.next();
newList.add(integer);
iterator.remove();
}