Help explain the code with line comments
public class CompletedList implements ListADT, Iterable
{
//Three instance variables
protected int count;
protected int modChange;
protected DoubleLinearNode head, tail;
//head and tail set to empty count set to zero
public CompletedList() {
head = tail = null;
count = 0;
}
//Override for head and tail, remove first number of list
@Override
public T removeFirst() throws NoSuchElementException
{
//if head is empty return error
if(isEmpty())
throw new NoSuchElementException("The collection is empty");
//Temp for each number set to head item
T temp = head.getItem();
//if first number equals last they are null
if(head == tail)
{
head = tail = null;
}
//else the ne
else if(head.getNext() == tail)
{
head.remove();
head = tail;
}
else
{
head = head.getNext();
head.getPrev().remove();
}
count--;
modChange++;
return temp;
}
@Override
public T removeLast() throws NoSuchElementException
{
if(isEmpty())
throw new NoSuchElementException("The collection is empty");
T temp = tail.getItem();
if(head == tail)
{
head = tail = null;
}
else if(head.getNext() == tail){
tail.remove();
tail = head;
}
else
{
tail = tail.getPrev();
tail.getNext().remove();
}
count--;
modChange++;
return temp;
}
@Override
public T remove( T element )
{
if(isEmpty())
throw new NoSuchElementException("The target is not in the collection");
if(tail.getItem().equals(element))
{
return removeLast();
}
for (DoubleLinearNode current = head; current != null; current = current.getNext())
{
if(current.getItem().equals(element))
{
if(current == head)
{
return removeFirst();
}
else
{
count--;
modChange++;
return current.remove();
}
}
}
throw new NoSuchElementException("The target is not in the collection");
}
@Override
public T first()
{
if (isEmpty())
throw new NoSuchElementException("The collection is empty");
return head.getItem();
}
@Override
public T last()
{
if (isEmpty())
throw new NoSuchElementException("The collection is empty");
return tail.getItem();
}
@Override
public boolean contains( T target )
{
if(isEmpty())
return false;
if(tail.getItem().equals(target))
{
return true;
}
for (DoubleLinearNode current = head; current != null; current = current.getNext())
{
if(current.getItem().equals(target))
{
return true;
}
}
return false;
}
@Override
public boolean isEmpty()
{
return count == 0;
}
@Override
public int size()
{
return count;
}
@Override
public Iterator iterator()
{
return new ListIterator(head);
}
@Override
public String toString()
{
StringBuilder sb = new StringBuilder();
for (DoubleLinearNode current = head; current != null; current = current.getNext())
{
sb.append(current.getItem()).append(' ');
}
return sb.toString();
}
private class ListIterator implements Iterator
{
private DoubleLinearNode current;
private int modNum;
public ListIterator( DoubleLinearNode node)
{
this.modNum = modChange;
this.current = node;
}
@Override
public boolean hasNext()
{
if(this.modNum != modChange)
throw new ConcurrentModificationException("The collection.
Help explain the code with line comments public class CompletedLis.pdf
1. Help explain the code with line comments
public class CompletedList implements ListADT, Iterable
{
//Three instance variables
protected int count;
protected int modChange;
protected DoubleLinearNode head, tail;
//head and tail set to empty count set to zero
public CompletedList() {
head = tail = null;
count = 0;
}
//Override for head and tail, remove first number of list
@Override
public T removeFirst() throws NoSuchElementException
{
//if head is empty return error
if(isEmpty())
throw new NoSuchElementException("The collection is empty");
//Temp for each number set to head item
T temp = head.getItem();
//if first number equals last they are null
if(head == tail)
{
head = tail = null;
}
//else the ne
else if(head.getNext() == tail)
{
head.remove();
head = tail;
}
else
{
2. head = head.getNext();
head.getPrev().remove();
}
count--;
modChange++;
return temp;
}
@Override
public T removeLast() throws NoSuchElementException
{
if(isEmpty())
throw new NoSuchElementException("The collection is empty");
T temp = tail.getItem();
if(head == tail)
{
head = tail = null;
}
else if(head.getNext() == tail){
tail.remove();
tail = head;
}
else
{
tail = tail.getPrev();
tail.getNext().remove();
}
count--;
modChange++;
return temp;
}
@Override
public T remove( T element )
{
if(isEmpty())
3. throw new NoSuchElementException("The target is not in the collection");
if(tail.getItem().equals(element))
{
return removeLast();
}
for (DoubleLinearNode current = head; current != null; current = current.getNext())
{
if(current.getItem().equals(element))
{
if(current == head)
{
return removeFirst();
}
else
{
count--;
modChange++;
return current.remove();
}
}
}
throw new NoSuchElementException("The target is not in the collection");
}
@Override
public T first()
{
if (isEmpty())
throw new NoSuchElementException("The collection is empty");
return head.getItem();
}
@Override
public T last()
{
if (isEmpty())
4. throw new NoSuchElementException("The collection is empty");
return tail.getItem();
}
@Override
public boolean contains( T target )
{
if(isEmpty())
return false;
if(tail.getItem().equals(target))
{
return true;
}
for (DoubleLinearNode current = head; current != null; current = current.getNext())
{
if(current.getItem().equals(target))
{
return true;
}
}
return false;
}
@Override
public boolean isEmpty()
{
return count == 0;
}
@Override
public int size()
{
return count;
}
@Override
5. public Iterator iterator()
{
return new ListIterator(head);
}
@Override
public String toString()
{
StringBuilder sb = new StringBuilder();
for (DoubleLinearNode current = head; current != null; current = current.getNext())
{
sb.append(current.getItem()).append(' ');
}
return sb.toString();
}
private class ListIterator implements Iterator
{
private DoubleLinearNode current;
private int modNum;
public ListIterator( DoubleLinearNode node)
{
this.modNum = modChange;
this.current = node;
}
@Override
public boolean hasNext()
{
if(this.modNum != modChange)
throw new ConcurrentModificationException("The collection has been modified!");
if(this.current != null)
{
return this.current.getNext() != null;
}
else
6. {
return false;
}
}
@Override
public T next()
{
if (!this.hasNext())
throw new NoSuchElementException();
this.current = this.current.getNext();
return this.current.getItem();
}
@Override
public void remove()
{
if(current == head)
{
modNum++;
removeFirst();
current = head;
}
else if(current == tail)
{
modNum++;
removeLast();
current = tail;
} else
{
modNum++;
modChange++;
current = current.getNext();
current.getPrev().remove();
}
}
