ConcurrentModificationException with iterator

robert trudel :

In a DTO I have

public class ProductTypesDto extends BaseDto {
  private List<Integer> colors = new ArrayList<>();
  ...
}

In my beans

@Entity
public class ProductTypes 
   @ManyToMany
   private Set<Colors> colors = new HashSet<>();
   ...
}

An user can add and remove colors for a productTypes

In a DTO to bean conversion, I do

private void convertToBeans(ProductTypesDto dto, ProductTypes beans) {
    //add element
    for (Integer color : dto.getColors()) {
        if (beans.getColors().stream().noneMatch(e -> Objects.equals(e.getId(), color))) {
            Optional<Colors> optColors = colorsRepository.findById(color);
            if (optColors.isPresent()) {
                beans.addColor(optColors.get());
            }
        }
    }
    //remove element
    for (Iterator<Colors> iterator = beans.getColors().iterator(); iterator.hasNext();) {
        Colors color = iterator.next();

        if (dto.getColors().stream().noneMatch(e -> e.intValue() == color.getId())) {

            Optional<Colors> optColors = colorsRepository.findById(color.getId());
            if (optColors.isPresent()) {
                beans.removeColor(optColors.get());
            }

        }
    }
}

when code is running, i get

java.util.ConcurrentModificationException: null

Seem like get this on iterator.next();

csunday95 :

Try doing

iterator.remove()

in place of

beans.removeColor(optColors.get());

see the documentation for remove(). Note the comment

"The behavior of an iterator is unspecified if the underlying collection is modified while the iteration is in progress in any way other than by calling this method."