MarbleCollection

package com.company;
import java.util.ArrayList;
    public class MarbleCollection {
        private ArrayList<MarbleSet> sets;

        public MarbleCollection() {
            sets = new ArrayList<MarbleSet>();
        }

        public void addSet(MarbleSet theset) {
            sets.add(theset);
        }

        public int getTotalMarbles() {
            int total = 0;
            for (MarbleSet i : sets) {
                total += i.getNumber();
            }
            return total;
        }

        public int removeColor(String marbleColor) {
            int total = 0;
            ArrayList<Integer> removal = new ArrayList<>();
            for (int i=0; i < sets.size();i++) {
                if (sets.get(i).getColor().equals(marbleColor)) {
                    total += sets.get(i).getNumber();
                    removal.add(i);
                }
            }
            for (int j:removal) {
                sets.remove(j);
            }
            return total;

        }
    }
}