Ok so I have an integer ArrayList from which I want to remove the entries that are either odd or are bigger than 100. My code, however, does not work and I do not really get why?

list.add(1);
        list.add(899);
        list.add(5);
        list.add(647);
        list.add(4);
        list.add(804);
        list.add(103);
        ArrayList<Integer> list2  = removeEntries(list);

public static ArrayList<Integer> removeEntries(ArrayList<Integer> list1) {
        for(int i = 0; i < list1.size(); i  ) {
            while(list1.get(i) % 2 != 0 || list1.get(i) > 100) {
                if(i != list1.size()) list1.remove(i);
            }
        }
        return list1;
    }

This does not give me the right list2-entries but I do not understand as to why...

CodePudding user response：

List#removeIf

Use the Collection#removeIf method, inherited by List. Pass a Predicate with your criteria for removal.

Like this:

list.removeIf(x -> x != null && (x % 2 == 1 || x > 100));
System.out.println(list);  // [4]

CodePudding user response：

The while loop in your method is incorrect, this should be an if:

List<Integer> filteredList = new ArrayList<>();
for (Integer i : list1) {
    if (i % 2 == 0 && i < 100) {
        filteredList.add(i);
    }
}
return filteredList;

Pretty sure using remove() while you're iterating through a collection will throw a ConcurrentModificationException.