/**
* Adds an element to the list, inserting it at the given position. The indeces of elements at and
* after that position must be updated accordignly.
*
* <p>If the index is negative or greater or equal than the size of the list, then an appropriate
* error must be returned.
*
* <p>If a null object is provided to insert in the list, the request must be ignored and an
* appropriate error must be returned.
*
* @param index the position at which the item should be inserted in the list
* @param item the value to insert into the list
* @return an ReturnObject, empty if the operation is successful or containing an appropriate
* error message otherwise
*/
public ReturnObject add(int index, Object item) {
ErrorMessage error1;
ReturnObject returnobj;
if (item.equals(null)) {
error1 = ErrorMessage.INVALID_ARGUMENT;
} else if (index < 0 || index >= size_list) {
error1 = ErrorMessage.INDEX_OUT_OF_BOUNDS;
} else {
error1 = ErrorMessage.NO_ERROR;
}
if (error1.equals(ErrorMessage.NO_ERROR)) {
Element elem = startElement;
for (int j = 0; j < index + 1; j++) {
elem = elem.getNext();
}
Element newElement = new Element(item);
newElement.setNext(elem.getNext());
elem.setNext(newElement);
size_list++;
returnobj = new ReturnObjectImpl(item);
} else {
returnobj = new ReturnObjectImpl(error1);
}
return returnobj;
}
/**
* Returns a list with the elements in this list except the head. The elements must be in the same
* order. The original list must not change or be affected by changes in the new list.
*
* <p>If the list is empty, another empty list is returned.
*/
public FunctionalList rest() {
ErrorMessage error1 = errortype(0);
FunctionalList list1 = new FunctionalLinkedList();
if (error1.equals(ErrorMessage.NO_ERROR)) {
// list1.setList(this.getList());
list1.remove(0);
return list1;
} else {
return list1;
}
}
/**
* Returns the element at the beginning of the list.
*
* <p>If the list is empty, an appropriate error is returned.
*
* @return a copy of the element at the beginning of the list or an error if the list is empty.
*/
public ReturnObject head() {
ErrorMessage error1 = errortype(0);
ReturnObject returnobj;
if (error1.equals(ErrorMessage.NO_ERROR)) {
Element elem = startElement;
returnobj = new ReturnObjectImpl(elem.getNext().returnObject());
} else {
returnobj = new ReturnObjectImpl(error1);
}
return returnobj;
}
/**
* Returns the element at the given position.
*
* <p>If the index is negative or greater or equal than the size of the list, then an appropriate
* error must be returned.
*
* @param index the position in the list of the item to be retrieved
* @return the element or an appropriate error message, encapsulated in a ReturnObject
*/
public ReturnObject get(int index) {
ErrorMessage error1 = errortype(index);
ReturnObject returnobj;
if (error1.equals(ErrorMessage.NO_ERROR)) {
Element elem = startElement;
for (int j = 0; j < index + 1; j++) {
elem = elem.getNext();
}
returnobj = new ReturnObjectImpl(elem.returnObject());
} else {
returnobj = new ReturnObjectImpl(error1);
}
return returnobj;
}
/**
* Returns the elements at the given position and removes it from the list. The indeces of
* elements after the removed element must be updated accordignly.
*
* <p>If the index is negative or greater or equal than the size of the list, then an appropriate
* error must be returned.
*
* @param index the position in the list of the item to be retrieved
* @return the element or an appropriate error message, encapsulated in a ReturnObject
*/
public ReturnObject remove(int index) {
ErrorMessage error1 = errortype(index);
ReturnObject returnobj;
if (error1.equals(ErrorMessage.NO_ERROR) && size_list > 0) {
Element elem = startElement;
// Element elem2=startElement;
for (int j = 0; j < index + 1; j++) {
elem = elem.getNext();
}
elem.setNext(elem.getNext().getNext());
returnobj = new ReturnObjectImpl(elem.getNext().returnObject());
size_list--;
} else {
returnobj = new ReturnObjectImpl(error1);
}
return returnobj;
}
public boolean hasError() {
return (errorMessage.equals(ErrorMessage.NO_ERROR) == false);
}
