JO

public class DynamicStringList implements DynamicStringCollectionMethods {

    private DynamicStringListElement first;
    private int length = 1;

    private  DynamicStringListElement getListElement(int index) throws DynamicStringCollectionException {  //durch alle Elemente durchgehen bis zum richtigen Element
        if (index < 0 || index >= length){
            throw new DynamicStringCollectionException(index);
        }
        if (first != null) {
            DynamicStringListElement element = first.getNext();//ToDo:NullPointerException(solved?)
            for (int i = 1; i < index; i++) {
                element = element.getNext();
            }
            return element;
        }else{
            throw new DynamicStringCollectionException(index);
        }
    }

    @Override
    public void append(String value) {
        try{
            this.insert(value, length);
        }catch (DynamicStringCollectionException e){
            e.printStackTrace();
        }

    }

    @Override
    public void insert(String value, int index) throws DynamicStringCollectionException {
        //next vom element übernehmen und element auf neues element verweisen lassen
        DynamicStringListElement newElement = new DynamicStringListElement(value);
        if (index == 0){
            if (length > 0){
                newElement.setNext(first);// müsste nicht das alte first auch eine neues Next bekommen
            }
            first = newElement;
        } else {
            if (index < 0){
                throw new DynamicStringCollectionException(index);
            }else {
                DynamicStringListElement element = this.getListElement(index);//ToDo: prüfen, dass es nicht kleiner null wird
                newElement.setNext(element.getNext());
                element.setNext(newElement);
            }
        }

        length++;
    }

    @Override
    public String get(int index) throws DynamicStringCollectionException {
        if (length == 0){
            return null;
        }else{
            return getListElement(index).getValue();
        }
    }

    @Override
    public void delete(int index) throws DynamicStringCollectionException {
        DynamicStringListElement deletedElement = this.getListElement(index);
        if (index == 0){
            first = deletedElement.getNext();
        }else{
            DynamicStringListElement element = this.getListElement(index - 1) ;
            element.setNext(deletedElement.getNext());
        }
        length--;
    }

    @Override
    public int getLength() {
        return length;
    }
}