java.util.ConcurrentModificationException: null

This error happens when removing an element in a for- loop.  Using an iterator and its remove method then the error will be solved.


using an iterator to solve the concurrent modification exception, caused by using for loop.

            for (Iterator it = foundCopy.iterator(); it.hasNext();) {
                Yard yard = it.next();
                if (checked.contains(yard.getInterest())) {
                    it.remove();
                }
            }

Or usign java 8, streaming and then filtering.